I am curious to find out if the new RTSP streaming is a little more CPU friendly. I have observed that at 7-9 FPS, zmc seems to use about 20-30% of the CPU on an Athlon 64 3200 -- and about the same for an X2 3800 (basically the dual core of the same processor.) Unfortunately, I currently do not have any cameras which output any rtsp streams to compare processor utilization against http streams.
If it is a significant difference, it may be enough reason for me to try and hack together an mjpg-streamer rtsp output plugin for those of us using web cams as video sources. =)