I'm going to get the Nitro Smartkleen NC22, I've done comparisons with the Nitro NC31/32/51 and it looks like most of the parts are the same (pwr supply, pump, impeller, intakes, bottom lind filter bag, impeller cover, drive tube mount, and drive motor v2) but not the wall climbing models.
Local merchant has it for $399. I know Cosco has the similar model for $299 and on line can be found between those prices. Merchant has 30 day policy and seem to be pretty good people.
I'll post a review and some pictures.
Manufactures produced video: http://www.youtube.com/watch?v=M-lB89AdUkA
Most of the info seems correct.
I'm removing my Recommendation. First unit lasted 2 years, 2nd unit lasted 14 months. Comes with a 12 month warranty. (Thank goodness for VISA extended Warranty)