Just attended a Rational demo. Seems VERY powerful but not quite as user friendly as others. But it does have this cool functionality that allows you to correlate test cases with configurations that it needs to be tested on.
If you have any specific questions I'll do my best to answer.
Got a question for you, I believe that Rational Team Test includes Rational Robot, I believe this module is a client/server automated testing tool with web testing capability, how powerful is this feature? Can you use this to extensively test a web site?
If you look in the Robot forum I posted a reply to questions regarding Robot.
Also see www.dundee.net/sqa/ then click on the click here link in the archives section then click view without joining (something like that) and you have a rational robot/teamtest/teststudio forum