I had a play with 4 zones today (Main PC, HTPC to the Yami's 5.1, HTPC to the Zone 2 Outside 2.0, and ID). It all worked pretty well (the whole not synced stuff is enough to send you schizophrenic however):
Nice and easy to link the zones
The "good old" Web Remote on my HTC Phone worked well
Don't drag zones in and out of the Link while stuff is playing (it tends to crash MC) - set up the links first then start playing content. Also determine which one you want as the primary zone and then just drag the others onto it....because
While you can still control stuff in each zone separately this is a bad idea as you quickly end up with different content playing somehow even though they are "linked". It is best to use use the primary zone to pause/play, FFD etc. That said, one benefit of having access to the controls for each zone is individual control of Vol (and it worked well from Web Remote) - doing anything else in these linked zones seems to cause grief IMHO. Even trying to adjust Link Timing on the ID caused it to skip ahead to the next track but left the primary zone still playing the previous track.
Thanks
Nathan