I see rainbows, but that isn't the reason. They really aren't that bothersome in the HD2s these days--although with NTSC material, can be an issue.
DLP, with all its sharpness, has an inability to create a smooth, film-like picture. It looks "fake" after awhile, and the sharpness starts to bother me. That sharpness also means I can't watch it for 5 hours (ie. college football) straight without my eyes starting to strain. I wouldn't call it headaches, but the picture is somewhat fatiguing. It is the antithesis of a CRT at times.
I have always wanted to try a DILA, and now prices are comparable to DLPs so I can. No rainbows, better color, and more film-like. Of course, contrast is going to be a bigger issue. That said, I owned a PLV-70, and the contrast wasn't too big a deal.
Also, i can get an anamorphic lens if i wish that will give 1400x1050 resolution for HD that should be spectacular. Problem is a might need a scalar to do it all, so gonna take baby steps first.
ps. I will run HD and DVD (via dvi) as my sources.