I know this is an old thread, but I noticed a lot of passionate reactions (surprisingly negative) to the query... just not, apparently, from anyone who'd actually used it.
I've used seamless for years and found no better instant setup, extremely high quality screen material, and at a very tiny fraction of the cost of professional screens. The surface is exceptionally smooth, allowing for the highest possible sharpness your media can deliver. It's also bright and free of hot-spots.
Because it's paper, it requires forethought (and a good flat wall) when doing outdoor screenings on windy evenings. That's been the only challenge I've dealt with in using it.
My 9-foot wide roll of Savage Super White seamless lasted more than five years before the 12-yards ran out - often running 16mm Scope films on the seamless unrolled sideways, presenting an impressive 9' x 23' image. (16mm Scope is a tad wider than 2.40) For a $30 investment, I can't imagine a better deal.
Just ordered a Da-Lite Model C 58" x 104" HCMW to pair with my Epson 8350 because the black levels on the Epson aren't as deep as those on film, but for film presentation, I'll always return to white seamless for its quality as well as for its economy.