I've used CodeCollaborator (the SmartBear software plugged at the end of the post) and found it to be a good tool for doing multi-site code reviews. It's straightforward to use; web based; the default diff tool is reasonable; you can specify suggestions or bugs i.e. "I think you should change this line" versus "This line needs to be changed".

IBM stuff, however... well, I've mentioned my feelings on their software on HN before. They're still selling Lotus Notes and Clearcase - I'd be very careful before taking anything they've built/bought.