No Mac Support
Video doesn't work between iPhone and a Mac desktop client, although it does seem to work with a Windows PC. A massive oversight in my opinion. Messenger for Mac is under supported and hasn't had an update in an age, and the last few updates have been tiny bug fixes. Nothing new added since Beta 2 in 2007!
Messenger 3 was a rewrite by Tristan O'Tierney (from the Colloquy project) who was brought in to bring the Mac client up to scratch. He was only given one other dev to help him. He left in 2007 and when people complained on his blog about the lack of updates to Messenger he replied, "Feel free to direct your complaints to people at yahoo - I’m no longer with the company. Part of my frustration was with the stagnation of the project.".
I need iPhone to Mac video calls, but I'm not holding my breath for video between iPhone and Mac ever to work. Messenger for Mac is a dead project as far as Yahoo is concerned.