I called a contact who has Skype 4.1 on Windows earlier today. The video call button was there, but the video didn't work. I'm having them download 4.2 and will try again.

As I've mentioned previously, if you disable and reenable the skype account on the N900, you should be able to IM offline contacts. I think it reverts to being broken after a reboot, though.

Edited to add: I can now confirm that yes, it works great as long as the other person has Skype 4.2.