I got a set as swag for DMing the Goodman Games tournament, and another set at a steep discount when I stopped by the booth to thank the maker. (If you heard C-3PO's voice just now, you're a huge geek.)
Each set contains about 45 one-inch walls -- hinges on one side, posts on the other -- that link together and stand in strings. As the name implies, the strings of walls are bendable at the hinges, theoretically making for fast set-up. Each wall piece is molded of gray plastic in a flagstone pattern. There's no paint-job to speak of. Each set also contains five -- not eight, as mentioned above -- free-standing doors. One set is enough to make -- approximately -- two 20 foot by 30 foot rooms, with doors, and a 30 foot connecting corridor.
The same product was offered in metal at last year's GenCon for $50 a set.
I haven't tried these in a game yet (will be on Saturday or Sunday), but I suspect they'll work out pretty well, though I'm not certain they'll add enough to make even the easy set-up worthwhile.
Also, there's substantial pre-use time, if you want the best possible hinge-post fit. I spent about 45 minutes at GenCon using a sharp pocket knife to clear flash out of posts and shave down hinges so that there would be full range of motion. (If you don't do this, the hinges will slip from the posts at angles approaching 90 degrees, or possibly even break.)
Are they worth $20 a set? Well, I can't know for certain, but my initial thought is "probably not." On the other hand, I'll be surprised if I don't find them worth $10 a set, and I wouldn't be too surprised if I find myself willing to go a higher.