It's worth what they're asking for it. I have an Optoma all-in-one and it's great for family viewing. We take it on vacation, to friends' homes, our backyard, virtually anywhere we'd like to watch a movie. We can literally take it out of its case and be watching a movie in less than 5 minutes.
The 300:1 contrast does seem absurdly low, but I will say that the contrast is not particularly good. When I was looking to buy, I looked at LCDs from Epson and DLPs from Radio Shack and Optoma. The Epson had all the features I was looking for: better sound, and more placement options due to a longer zoom. Unfortunately, I liked the picture from the Optoma Movietime much better. It was definitely a more washed out picture on the Epson. On the other hand, most people who have these are thoroughly thrilled with them. And I would probably be happy with it as well. Ours never fails to elicit all kinds of WOWs from the crowd.
For ease of use these things can't be beat. Sure you can buy a far better picture from another projector, but what you lose is the portability. If that's what you want in a projector, these things are great. Epson also makes a 720p unit, but it's going for about twice the price that HH Gregg is selling the 50 for. For the amount they want for it, I think it's an excellent buy. If you do buy it, I'm certain you'll get an enormous amount of enjoyment out of it.
By the way, the screen I normally use outdoors is a Gemmy inflatable screen. It lists for around $200. It takes longer to set up than the projector, but it sure looks cool. I've also used sheets, table cloths, shower curtains, walls, and this summer I'll probably find a few more surfaces to project it on.