Wes,
Hopefully you will also consider RCS (Residential Control Systems)
http://www.resconsys.comin addition to Aprilaire. I think both are fairly popular with the home automation crowd.
As a side note, using the ElkM1 plugin, I have already designed a nice screen that controls and displays multiple Tstats and zones, but I bet the stuff you guys come up with will be a bit fancier.