I bought a lightly used Necky Manitou 13 off of Craigslist the day before yesterday, and, taking out for the first time last night, figured I'd post a review.
First, 12 feet, 10+ inches is both shorter and longer than I imagined, even after eliciting the help of a tape measure. At 45 pounds, the Manitou is almost a joke to pick up and move solo (I'm 27, 6', 145 lbs., swimmer's build), and really doesn't seem like an object nearly 13 feet long. That said, two inches longer and there'd be no way to get it up the stairs to my third floor apartment. It fits so-so in the back of my regular cab Colorado (6 foot bed). Being bright red on the prow means I don't need to tack on a flag, but even with the tailgate down, 5 feet of kayak hangs out (I have a hard tonneau cover, so there's no other way for me to transport it).
As far as performance goes, I've only ever used an inflatable tandem before (and that, only twice), but the Manitou feels fast, fast, fast. According to the GPS, I got it up to just shy of 6 MPH in short bursts, and my two 1.5 mile circuits of Park Lake took a little less than an hour, including time spent goofing off, watching people fish, and back-paddling to look at this, that, and the other. The Manitou tracks straight as an arrow—so straight, in fact, that I think it might be a little difficult to navigate any particularly twisty rivers. It's also very stable—the only way I came close to tipping it was when I was getting out. The foot pegs are nice to push against, easy to adjust, and help you keep your knees pressed against the knee braces. The seat is couchy, but I need to make a few adjustments when I have time to figure out all the straps (none of which seemed to get in the way of paddling, etc).
Regarding the hatch, follow the advice posted below about using your knee as a third hand. Simply hook one end of the neoprene seal under the lip, hold it in place with your knee, and stretch it over to the other side—takes all of five seconds. The guy I bought it from said the hatch is water tight—unless you roll it—even without the seal, but I've not tested that.
My only complaint—and this may simply be due to ignorance on my part—is that the slot for securing the paddle to the boat is behind the seat, rather than in front. I can't for the life of me figure out how to put the paddle in there while under way (if I wanted to, say, stop and have a sandwich).