Just installed the 6.0 client I downloaded from Remedy's website.
Installed under CW 4.1 without a hitch.
I'm running the alerter and the user client without any issues so far.
There's one quirk that I haven't determined if it's a CW or Remedy bug yet, but when double-clicking on a ticket within a search, the new window is popped up in the background, instead of the foreground. I haven't seen any options that would modify this behaviour although I could be missing it.
Other than that, it seems to work just fine.