1) I think (a) System #1, but individual room control of sources would be a big feature. Meaning, if you had a concrete older home but wanted to retrofit distributed audio, a wireless solution would be nice, but also being able to control rooms individually as well. I think Sonus has a nice distribution system, but what they lack is integration with the main system. You have to load your music /through/ the Sonus, versus just having the music play off your computer. I think for mass market your going to need to make it as easy as possible, maybe some way to integrate with a typical IR universal remote or something.
2) Somewhat interested. I've almost purchased wireless systems just to 'try' them in other rooms, #3 will continue on this..
3) I'd try it first in my garage. I want to add streaming audio, but the concrete structure prevents me from running wires. I spend tons of time there, and have a self contained system, but it requires me to transfer to a drive and carry it down there. Which is alright, but skipping the extra step would be nice. Also, it would clean up my garage...which is (strangely) a very high priority for me...my garage is as clean as my living room (which super clean), so nixing the wires is big to me.
As a side note, I think wireless is a really popular solution for the future. Maybe not for dedicated systems, or audiophiles, but for distributed audio it makes a lot of sense.