Are you saying Sweden and Austria are even cheaper?
If so, that's great and all, but honestly, from an American perspective, EUR15 per month for 3GB of data is a very, very good deal. That's so cheap that I'm not sure I'd care much if another place was even cheaper.
I didn't notice any coverage problems while I was there, but admittedly I was only there 2 weeks, but I did take the trains a lot (but only in Bavaria). I never noticed any problems. I was using O2. I don't think the coverage was perfect all the time, but it's not perfect here in the US either, and I use Verizon which is generally accepted to have the best overall coverage nationwide.
In short, I think Germany has things pretty good from a global perspective, as far as cellphones go. Some other European places may be even better, but I just don't see much to complain about over there, when compared to any place outside of Europe.