I have been using the wireless Internet service
Mobile Unlimited from Swisscom, it connects to the Internet basically anywhere my mobile phone works. I haven't had the chance to use it on a train yet but I don't see why it wouldn't work any less than the phone does. Maybe if I have time tomorrow I'll jump on the train with my laptop and give it a try.
Here's a picture of the modem that I got from Swisscom:
Swisscom offers data transmission with these technologies:
HSPA up to 7,2 Mbit/s
UMTS up to 384 Kbit/s
EDGE up to 256 Kbit/s
GPRS up to 53,6 Kbit/s
Public WLAN up to 2 Mbit/s
WLAN up to 54 Mbit/s
With the following coverage % in Switzerland:
99.8 % EDGE/GPRS
90 % UMTS
45 % HSPA (90% until the middle of 2008)
PWLAN > 1000 hotspots
The Hotspots are cool because you don't even need to use the modem if you have wireless built into your Laptop already. Even with the modem I was really surprised to see download speeds comparable to DSL lines.