i am surprised though that you wouldnt pick arsenal group as one of the hardest, cause well porto is not a bad team and cska has showd potential before, hamburg obviously dissapointed totally, but because of their injury problems.
but with all the honest, group A, well yeah bremen showd especially last year that they are a though team, no doubt about that, but well the quality of chelsea and barca squad is just so much better. i wouldnt say though that i am totally surprised, although what i would say, is that chelsea seemed to "help" bremen a bit, i didnt see chelsea playing at their best against bremen, they looked unimpressive, couple of shots on goal, yeah, some lucky deflection from bremen defens, but overall, with the quality chelsea has, they didnt play as good as they can.