With Skype I can play games with a group and put the mic in always on mode. No feedback, no audio from speakers, and no keyboard clicks. It's pretty damned amazing to be honest.

Ventrilo and Mumble do have far superior support for massive number of people in a chat room. If you're participating in large MMO raids or Eve Online type festivities the Skype doesn't have the necessary features. For my ~5 player parties Skype blows everything else out of the water and isn't even close.