Rob - I'm in the same position. I have an L300U that I'd like to upgrade, and I've been following the 700 discussions closely. It seems to have nearly everything I'm looking for. Nearly.
Pretty much the only thing keeping me from eBaying my L300U and pre-ordering the 700: DUST BLOBS! So far I haven't read anything which indicates that the 700 is any better at avoiding ANNOYING dust blobs than the L300U. This is easily my biggest complaint about the 300, and it has nearly ruined me to any future projector that doesn't have a completely sealed light path. I'm sure that the CR, resolution, brightness, etc of the 700 would be a marked improvement to my 300 and therefore something that I would be thrilled about, but I also think that the first time I turn on my new $2k projector and see a big green blob on the screen I would feel like screaming. If I were going for another LCD, I would almost certainly choose the 700 over the Z3 or HS51, but I'm just not sure I can bring myself to do it.
Instead, I'm going to wait and read some reviews on the Z2000 and then go see one in person. Assuming reviews are good, and the in person viewing is good, and I don't see rainbows, and, and, and...the only thing that just *might* prevent me from purchasing is its lack of lens shift.
-tony