Hello,
another vistream brand is running in germany which has very nice roaming rates. The zones structure is compareable with sunsim and che-mobil but the rates are lower. You can buy the card for 20 Euro including the full 20 Euro of initial credit.
http://friends.vistream.de
Rates in germany:
landlines: 10ct/min
own net: 15ct/min
other networks: 20ct/min
SMS 15ct
GPRS 4,9 Euro/MB (100k-increments)
Roaming:
from and to Zone 1, 2 and 3: 39ct/min
incoming calls Zone 1, 2 and 3: 19ct/min.
Starting zones:
http://friends.vistream.de/Documents/Startlaender.pdf
landing zones:
http://friends.vistream.de/Documents/Ziellaender.pdf
This might be interesting for some travellers.