But are they standards-based? (Score 2)

I'd guess not. There are standards-based (RTSP and RTP/RTCP) servers available (PRISS, Darwin, and ELSA, for example - see streamingserver.org for more info), and clients in the works for Linux (I hope Sun is working on a RTSP layer for JMF; likewise, I hope Apple is porting Quicktime Client too). I'd bet that in a year's time, streaming multimedia will be the norm for all platforms, and companies like pixelon will stand out from the background noise only if they have something more than a window-only, single-media-source solution.