Now, I did have problems with this system. I sold 10 BTC's at 150 Euro and the price tanked shortly there after. The seller, decided not to pay and bitcoin.de automatically cancelled the transaction
after 24 hours. Not much I could do with a selfish crook like that. Anyway, I and probably others, complained and then they changed the confirmation time from 24 to 12 hours. These are just
growing pains.
Selling Bitcoins has some problems there, but for buying it's alright. You will have to wait some time for the Bitcoins though, so it's nothing for daytrading.