@bonemap I'd agree with all Russell says here. The other thing to watch out for with the ultra-short-throws is that they often have quite a large 'pitch', so if you place the projector on the floor it will project an image 'up' on to the wall; it's hard (or impossible) to get an image to reach the bottom of the wall because the angle of the mirrored lens has to shoot back past the body of the projector itself. Obviously if you are rigging/mounting it over head this is reversed and the image shoots 'down' leaving a gap at the top. This is a pain if, for example, you want to fill a wall with an image from floor to ceiling. Because of the extreme optics, as soon as you angle the projector off the horizontal things get messy quickly with the huge amount of keystone needed. Just something to watch out for and it obviously varies massively between makes/models especially at the budget/mid range prices.
Even with the top end kit it's an issue: the massively popular Panasonic DLE030/DLE035 lenses for the single-chip projectors have a huge pitch, dims A1/A2 in this diagram. The top-of-the-range D75LE95s for the three-chip monsters are slightly better, but it's still an issue. This can sometimes be even more a problem with flying cradles etc that make the body of the projector bigger and get in the way of the beam.
The Epsons mentioned above have a really clever lens, the EP-LX02 that looks like a periscope and bends back round under/over the body of the projector so you get a more traditional 'flat' projection without the pitch. It's probably the one department where the Epsons outperform the Panasonics in my opinion. They're very expensive though; looking forward to when that style of lens trickles down to the cheaper models, as it no doubt will at some point. There may well be some cheaper classroom 'whiteboard' style projectors that already do this.
On the wide but not crazy-wide side you can get projectors with a fitted lens that has a bit of a zoom for some flexibility. I just did a gallery install with a pair of BenQ W1210STs, they had a 0.69-0.83:1 zoom and did a lovely job, they're only 2k lumen but it was a very dark room.
