Ah, we've been keeping an eye on the Craigslist ads for one here for ages! They do pop up but usually have a motor that we don't want or something. The 12' is the "right" size I think. We'd like it as the spare dingy and the "beater" dingy.
We have a friend with the 12' square back (older ones have a back that comes in a bit) and uses a little Honda 2hp to go all over the place. They love it. We went with he and his wife on a major provisioning run and were amazed by how much stuff that thing could carry, too.
Their boat doesn't have a whole lot of deck space but they manage to get it put together onboard w/o a problem. They do so at anchor all the time. Practice.
Best to you