OK, pulled down git and built tsp's pvr client branch. Recordings seem to work well. The main issues for me are related to Live TV:
1. There appears to be some issues with the channel numbers. I noticed something similar with dteirney's plugin too. I have a cable connection from which I get local unencrypted (i.e. "clear") QAM channels. The myth backend, however, uses the subchannel notation when scanning and adding the channels (i.e. "2.1" for WGBH for example, see my posts on this thread, starting at page 42 or so: http://forum.xbmc.org/showthread.php?tid=82015&page=42
The PVR plugin does not appear to like it, and it appears to wrongly assign the channels. (i.e. it rounds "2.1" to "2", but when I try to play that channel, it's the wrong channel). This might be a PVR-wide issue, not just mythtv.
2. Sometimes (because of the wrong channel assignments), it attempts to play a "hidden" channel (at least hidden by me in the mythtv backend, because it was probably encrypted). When it tries to play some of these channels, it simply hangs, but pressing "stop" doesn't return back to the interface, it gets stuck and I have to manually kill xbmc.
Some other issues I noticed:
The interface pops up with "Next recording start time" timer event for a program that ended in 2010, in the popup on the main screen. It doesn't appear to check whether the program is actually in the future. (Again could be a PVR-wide bug).