I've had both the paint and the fixed screen and the screen wins hands down. Problem with the paint is not the paint itself, it's the fact that the surface of the wall is porous so you will always have slight bumps which on a HD picture certainly causes a degree of "pixelation" as it were.
I got my screen when I got my projector (from West Coast Hifi in Osborne Park) and it cost somewhere around the $700 mark for roughly 120" which compared with $6000 for the projector wasn't that bad considering the improvement it gave me over the special paint.
Make sure you get a good HDMI cable (or whatever signal type you are using)
