had both the dct and manual E92 coupe M3 ... DCT and dont look back ... im a manual guy but the dct makes the M3 ... DCT is also resale wise a lot better than manual ...
2007 M3 Manual: Mdynamic, white with CF roof, 19's, front /rear pdc, logic 7
2008 M3 DCT: 19"s, white with cf roof, logic 7, usb ipod connector
i had one of the 1st ones that came out with the DCT box and with new tech you expect glitches. There were 2 software glitches, the one was a delay between upshifting and the gearbox deciding it needs to change ... the other during spirited driving and coming to a stop sometimes the car remained in what ever gear it was in, no matter you trying to upshift or downshift the car would not listen to any of your commands ... when the car came to a full stop and you tried to drive off, the car would then jump in neutral ... all this was sorted out by a software update ... so if the car you intend buying is not new but a april/may 2008 model make sure the box has been updated ...
Just also note, when buying an M3 its very important what options the car MUST have ... without these options resale is heavily affected:
1. 19" wheels a must ... ( i recall a dealer having a dct mdynamic M3 fully loaded, with cf roof and it was white but had 18's, the dealer could not sell this car because of this and they had to buy the 19's from Germany in order to make the car sellable ...)
2. If the car is silverstone/white/space grey it MUST have the CF roof option, having a s/r hurts resale again with these colours
3. Red is not popular
4. If you can you have to take the DCT box, compare the resale for a dct coupe with 19"s vs an m-dynamic manual loaded ... the DCT even though it costs less new than a very well spec'ed manual, will have better resale
5. Try to avoid the 4 door model for resale purposes
Regardig your question
Day to day driving: The DCT is very easy to live with, nothing simply, the car can be left on D mode
spirited driving: DCT again, its just so much fun

... having both hands on the wheels while attacking a corner is awesome, the downshift is music to ones ears with the throttle blip ...