Take the follow FWIW -
I had a similar plan ... three projectors in my basement home theater room. I already had two of the three so figured my investment wouldn't be too much more... figured the best way to check it out was buy another HD20 at bestbuy, try it for a week or two, and if I didn't like it, return it....
My goal was to have an eyefinity gaming setup (like you've mentioned) and my own mini sports-book.... after trying it all for two or so weeks I ended up returning the 3rd projector.
This was the main reason:
I tend to prefer a desk with keyboard and mouse for my gaming, so it worked out better for me anyhow, though occasionally I'll game on the projector ...
Burnitdown and I are the same here... gaming on that big of a screen was a PITA for most games and honestly took down the fun factor. For the few times I would like to game on a big screen one 120" screen is enough.
My current setup has the 120" screen, 92" screen to the side (only really used for sports)... 3 couches to view the screens, and behind the center couch a desk that holds my PC (HTPC / Gaming rig) and monitors. I have an hdmi splitter on the output so I can play using eyefinity, one monitor, or on the projector... I enjoy this setup the most since I can play games and still send movies to the projector.... Its great because I can fire up some movie for my fiance while I play games at the same time.