OK, others have answered some, or all of the points, but there are a few finite details missing. Forgive me if I happen to repeat what has already been said.
Automatic
1. When in auto mode, Im assuming the gears change quite early in the revs? Hence you should be able to get better MPG? Am I correct in assuming this? If so it would be perfect since I could use that to get to work and back, then shift it into manual for when I want some fun!
Yes and no!
You need to be aware that the DSG uses 'fuzzy logic' in its electronics, and has an 'adaptive' shift pattern. This basically means that the gearbox ECU can effective 'learn' your driving style, and will actually adapt the shift changes in auto to suit your style. Obviously, this all takes some time, and isnt instantaneous. So, to use the standard GTI as an example - before the 'box has learnt your driving style, under normal or moderate throttle openings, the box will have changed into 6th gear at around 32mph. Now, if you happen to be a driver who regularly likes to drive it like you stole it, ie giving it some welly, then the ECU will actually modify the shift patterns to change progressively higher up the rev range - so you may find that it may not go into 6th until say 60mph. The downshifts are also modified accordingly too - so if you are finding that 6th only appears with 60mph on the speedo, you will also get much better engine braking too, due to downshifts higher up the rev range.
This adaptive lark will never quite reach the shift pattern changes of sport mode though, and will never reach the red line (unless you have activated kick-down).
Manual
2. When using manual, I understand you can shift up/down with the Gear Knob, or the paddles (if you have them). However, is it true that if you reach the 'redline' on the revs, the car shifts up for you anyway?
Yup. Although technically, it shouldn't actually reach the rev-limiter.
3. Does the dash display the current gear you are in?
Yup - unless the dash panel insert is fooked!
Actually, I think different 'model year' cars have a slight difference in the display, and it is also slightly different between the midline and the highline computers.
4. If you are traveling in 4th Gear, and you come to a 2nd Gear corner, as you brake do you have to shift down or does the car shift down automatically as you brake? If you need to shift down yourself, does the car jolt as you shift down to a lower gear which doesnt match the revs?
The box will automatically change down as the revs get close to the idle speed. All downshifts like these are barely noticeable. However, if you downshift (or upshift) yourself, particularly in a manner 'opposite' to what the box was expecting, then you can 'confuse' the box, resulting in a small delay in shift change. It is extremely rare for the car to jolt whilst the vehicle is in motion. Jolting usually occurs when stationary, and you try to 'rush' the box.
5. Ive heard talk of the car jolting, and not being smooth, when using the manual transmission in lower gears - is this correct? If so, why does this happen and can it be corrected by the driver?
Not really common at all. See my answer to the above point.
6. When changing up a gear, do you need to remove your foot from the accelerator, and then put your foot down again - as you would if you had a clutch pedal - or do you just keep your foot where it is and not release the pedel at all?
Nope, you can keep the pedal burried in the carpet to the floor boards when changing up manually - and still get a nice smooth change. I would actually state that if you were to take your foot off the gas, then the quality of the shift would be noticeabley poorer - the DSG, just like all automatics, are actually designed to allow gear changes whilst still keeping the throttle open. You can also keep the pedal mashed to the floor when changing down - although the shift quality will be much harsher, and you may actually find a delay in shift change (because you have confused the box).
7. Is it correct that when in manual you cant change gear while turning, say around a roundabout, for example?
Nope. You can change the gear (if you so desire) anywhere from full left lock to full right lock, and anywhere in between.
Sport
8. So in this mode, the car is in automatic tranny, but takes the revs to the highest point between each gear change?
Yup. Dependent on oil temps (engine and box), it can go all the way to the red line. It also down changes much higher up the rev range too.
A bit of a moot comment though - try not to use sport mode in 30mph built up areas. Because you will probably be doing abou 5,000rpm in second gear at 30mph, it could appear to others as though you are driving in a bit of an 'anti-social' or agressive manner. So it is best to leave sport mode for NSLs, B roads and the like.
Oh, and NEVER use sport mode until the engine is at normal operating temperature. Whilst it is warming up, it is best to leave it in normal auto mode, as when cold, the auto shift times are programmed to change in a manner which helps the most rapid warm up of the engine.
9. Why would someone use this over the manual mode in that case? Since even with manual if you reach the top rev, it will shift up for you - just as sport does?!
Maybe they want to have some 'lazy' fun?! And don't forget, it is a good idea to simply check that it actually works too. And there may be others who just cant get on with the paddles or floor shift lever - my SWMBO hardly ever uses the paddles, but often uses sport mode. And don't forget the disabled - they are allowed fun too!
Launch Control
10. I understand you can use this with both Sport and Manual tranny modes - what happens if you use Launch Control with ESP still on?
It won't work. You'll just get a normal, but still rapid acceleration, but the traction control is likely to kick in.
11. When in sport or manual, by keeping your foot on the brake, bringing the car to 2400rpm, then letting go of the brake, do you automatically use Launch Control, or is there some other button etc to be pressed to inform the car you want to 'launch'?
Nothing else to twiddle with. And you can also keep the accelerator pedal mashed to the floor whilst holding it on the brakes, and, depending on what car you actually have, the electronics will just hold the engine revs at around 3,000 rpm (4motions slightly higher, diesels slightly lower). Once you release the foot brake, just keep the gas pedal to the floor, and when the front tyres grip, it will rev up to the red line in 1st before changing up. The electronics are still a bit 'nanny' though, in that they wont allow the front tyres to smoke on the spot on the red line whislt the rears are still stationary.
Overall
12. When changing between manual/auto/sport modes, do you need to bring the car to a stop, or can you change even while the car is moving?
Nope, you can change between any of the modes at any time - obviously whilst stationary or travelling in a forward direction. It you are reversing, and bang it into sport mode whilst still going backwards, your clutch packs might call for an early retirement.
Sorry for so many questions, but I want to fully understand DSG before I either get it, or rule it out.
No worries about asking questions. What I would say though, is to actually have a drive in it - a long drive, ideally an all day test drive, unaccompanied, so that you fully experiment, and get used to it. There is nothing more irritating than having some salesperson sitting in the car, and frowning at any slight error you may make.
The added bonus is that the wife only drives auto cars, so she could drive it as well - if I ever let her (although its a good arguement in convincing her that we want a GTI ) Although Im concerned that not having a manual will take all the fun away from driving, and make driving 'boring'.......
Whatever ANYONE eles says, having a DSG will NOT take away any fun from driving a normal manual. Look at my sig, and you will see I also have a V8 RS4 (which is a six speed Getrag manual, arguably the finest manual gearbox on the planet) - and both the RS4 and the GTI DSG can be equally enjoyable and rewarding to drive. If only the GTI came with a V8 soundtrack . . . .
