I've been using Teamviewer for a month now and it's pretty incredible compared to my past experiences with remote desktop tools. It's basically Remote Desktop + Skype (it navigates firewalls, has VOIP, etc.). No chat though. Highly recommended.
The only drawback that I think should be mentioned w/ Teamviewer is that it is only free for non-commercial use. As a RDP replacement it is awesome -- a friend and I troubleshoot problems that way sometimes. But it isn't free for those that would use it in a professional capacity.