Steffi,
I can't speak about the other bags mentioned here (I have heard good things), but the Ristretto is fantastic. I've had mine for over two years now, it gets a lot of use, and it stills looks like it did the day I got it. I actually just ordered an ID messenger with brain cell for daily/mac use. The Tom Bihn stuff is top quality. Knowing what I do now, I would wait the month or two. It's worth it. Let me know if you have any specific questions.