I'm not sure how much it would be advantageous for web  applications, and as far as I know it only works under Windows platform, but in a 4-tier total solution project in 2003 I'd setup Rational Robot for our test  team and made them work with it; They still use it, and I guess they live with it happily ever after ;)
I don't believe it will be a time consuming to see its benefits, I guess you can get the trial version:
http://www.ibm.com/software/awdtools/tester/robot/