I've driven both petrol and diesel DSG.
I've also been shotgun with Hurdy as he delivered an 8 minute lap in his DSG Golf5 GTI.
IMO they work better on diesel motors, as with (IIRC) seven gears the 'box can keep the motor in its sweet spot way more than a person with a 6-speed manual.
The flat-taps changes are simply epic and you will not replicate that rifle-bolt change quality with a manual 'box.
DSG also doesn't have the losses that conventional auto-boxes has.
BUT (and it's a big but if you're someone who wants to be 'involved' with the driving process) it is more like driving on a playstation, than a real car.
I didn't like it.
Personally I would only want a DSG with paddles on the wheel, otherwise you're just doing to put it in D and let it self-shuffle.
The Wife came to it squawking about not being able to drive an auto (
) and now would quite like the next daily to be DSG.
I think there were some failures on the early mech-a-tronics on the first ones, but when I've spoken to my VAG-tech mate he's not gone on about how cra-p they are.