In response to a question from my boss, I just wrote this email which summarises my opinion of the new Web Interface that Microsoft have included with Terminal Server on Windows 2008:
Err, it won’t work on a Mac, or Linux, or Solaris, or xxBSD, or Windows with Opera, or Chrome, or Firefox, or Safari, or anything except Internet Explorer.
I also experienced a problem using it from my home machine which is just running regular Windows XP Pro/SP3 which meant that I couldn’t enable the required ActiveX object without arsing around with the registry. The ActiveX object was there but disabled and hidden.
So my summary would be that if you happen to run IE on Vista SP1 then it will probably all be OK, otherwise there is a moderate chance that it will not work.
If you get the impression I don’t like the web interface you would be right 
A simple “No” would have been fine. I think we’ll be sticking with Citrix.