I built rc2 and used the pvops kernel pulled from git for dom0 (make 
linux-2.6-pvops-build).
dom0 runs much slower than the the vanilla kernel (without xen), and the 
system as a whole, including the domUs I'm running, seems sluggish.
More of a concern is that I'm getting random segfaults in the domUs. I 
have 2 domUs running: one using the 2.6.18-xen (built for 3.4.2), and 
another using kernel.org 2.6.32.7. I can't be sure it's not a hardware 
problem (as I've also upgraded my MB) but both the RAM (tested with 
Memtest86) and the HD (tested with the WD diagnostic tool) seem ok.
Here's a sample of the domU segfaults (I can't reproduce them - they're 
random):
gnome-panel[3232]: segfault at 7f5264a27390 ip 00007f5263a8205d sp 
00007fff74ce9630 error 4 in libc-2.10.2.so[7f5263a11000+14a000]
sshd[6373]: segfault at 000000ffadffd8ff rip 000000ffadffd8ff rsp 
00007fffb61abab8 error 14
At one point I was using the dom0 kernel for one of the domUs and that 
crashed a few times, so I switched to kernel.org's 2.6.32.7
The domU using 2.6.18-xen has always been rock-solid before under 3.4.2 
and earlier (it uses Debian Stable).
Let me know if you want log/config files.
 

Is your pv_ops dom0 kernel 32bit? Is your kernel.org 2.6.32.7 kernel 32bit? 
If yes, do you have CONFIG_HIGHPTE=y in .config?
-- Pasi