I used GT-sim in Lausanne and Geneva last week. No problem with sms and incoming calls (honestly I received only one call and i didn't pay for it!

)
08-12-2005 20:23 roaming in SWITZERLAND |<- incoming call 417869***** 0:00 0.38 0.00
Also I had lot of troubles for outgoing calls... I tried with Orange CH, Sunrise and Swisscom but I had the same problems. 1,2,3,10 times before to be connected!

I hope that this was only a swiss problem.