Service on a B7 might be a nightmare, I can't even imagine what some of the parts catalogue might cost on that. I wouldn't want to foot the bill. I've seen the new B7 live though, and it is amazing. The new 7 with the M pack is great too. The new 5, I'm pretty lukewarm on. It doesn't really look like a Bimmer from the back, and the front is a little confused looking.
I know the maintenance will be high, but I do a lot of the maintenance on my E46 so I should manage fine. I think I'd rather have this than any AMG so there's nothing else that could suffice as a substitute. I'm not a huge fan of large sedans except this B7 and some other AMG sedans, namely the black series.