I just got off the phone with Sonicwall Tech support. I called them to find out how we can resolve the error you get when you try to connect to our SSL VPN via Windows Vista. The support person (who was very nice BTW) didnt know what Windows Vista was. They say that it wont be supported until it RTM's. This is pretty amazing considering it's only a few months away and will be released heavily come the first of the year. They claim that the problem is with the Microsoft code base. However, the error generated by Sonicwall says "Client not supported." It would be nice if they were more proactive and posted something on their forums stating what the exact problem is and how they are working to resolve it. Saying that "Microsoft is messed up" makes no sense to me. Checkpoint SSL VPN works fine with Windows Vista.
This has been the major stumbling block for me adopting Vista completely. Otherwise Vista has been very stable and fun to use.