I hate the fact that the Mac Pro is always waiting for Intel's Xeons. I wish there was a alternative way to get the same performance and reliability. Personally I'd sacrifice the ECC ram, server based boards if I could get a 6 core sandy, lots of ram and everything else equal.
The 6-core Sandy's aren't out yet either so so far there has been zero extra waiting on a Xeon version. And from what it looks like, if there is a wait, I'd wait and give them time to fix the VT-d and maybe get C2 stepping going on the Xeons. Not sure if Intel cares for the consumer SB-E's.