When I got mine, I was in a similar position to be able pick my spec from the outset. Here's what I got/think:
Pearlescent paint (diamond black) - Beautiful, a must but a b!tch to keep clean and avoid scratching. Solution - get it professionally detailed and have the paintwork professionally corrected as/when - I've just booked this after my 2nd service in Sept.
18" Monza II's - Fabulous looking wheels which are perfect for the car. Do it - no question. I do not find the ride in any way harsh although the Dunlop Sport Maxx tyres are noisy (pot luck what tyres you actually get on the car from the factory).
DVD Sat Nav (MFD2) - Very expensive for a mediocre 2D unit which cannot do a full post code search and has no integrated speed camera database - common faults with manufacture units. There are many aftermarket or portable units which do the job as well or better (like my TomTom 730 Traffic), however I do like a standard appearance to my dash and the RNS510 seems to be the perfect answer. I got the iPod preparation in preference to the CD multichanger and I have to say I like it's performance with the standard speaker set up, but again, there is limited functionality in that it doesn't display any artist or track info, only playlists which are numbered 1 - 6 (1 - 5 are individual artists/albums but
you have to remember the order you programmed them and playlist 6 is the entire iPod content). The centre armrest in which the iPod player is located is also a useful addition.
Sunroof - bit of an indulgence with the car having aircon (but then I did come from a Boxster) but, from time to time, when we do actually get some sunshine, I like to have it open - the integrated airflow spoiler works OK at 70 but buffets slightly below that. Also good for ventilation when the dog is in the back !
MFSW with Highline Computer - Again, an indulgence but it does look good and the MFSW has some useful functionality (iPod playlist/radio channel/volume changes for the unit audio and phone, including a mute button). I am going to add the OEM factory bluetooth option (buying from a member of this forum - vRStu) and will fit it myself. It integrates with the DVD Sat Nav unit and has some (not all) functionality via the MFSW and Highline Computer display - much better than the Parrot option anyway. The Highline Computer is handy as you get the Sat Nav/audio and some of the warning indications replicated in the dash pod and it looks aesthetically better than the 'half display' unit of standard cars.
Bi-Xenon Headlights with auto washers (bigger washer bottle) and auto adjustment - Fabulous, very bright blue/white lights and much better illumination than standard lights. A must have option IMHO. I wouldn't be without them on any car from now on.
Winter Pack - Heated seats (thought they all had this), heated headlight washers and low water warning light (woopeee) - useful only in that the standard car doesn't have a low washer warning light (honest).
Overall, I don't regret anything and the only thing I might add would be the reversing sensors.
Remember - optional extras are to your personal preference and don't expect to get much of the additional cost back when you come to sell the car on - you should sell it easier though

Enjoy speccing your new car and the driving experience when you get it

Cass