I got it yesterday. Here's a review so far.
I haven't gotten used to it yet. The interface is very different, and it makes use of Sims2-style sorting mechanisms, which is kind of neat. However, my main complaint at this point is that you can't zoom out far enough. I want to see a larger portion of the city at a time, and you're so close to the action it's hard to plan roadways.
I think that Societies is aimed at a very different kind of gamer from the previous Sim City games. It's highly complex, but in a different sort of way. Gone are the days of finding the right tax rate balance, zoning large tracts of land and hoping people move in, and micromanaging city services. Gone, too, are the mundane details of transportation planning, the endless color-coded mini-maps, and the overlapping circles indicating police and fire coverage. The game takes care of these things for you.
Buildings are now placed individually -- including homes and offices -- so you can decide that the software developer goes here, next to the high-rise condos, with an ice cream parlor in between. Each building either generates or utilizes a variety of resources which must be kept in balance: workers with jobs, citizens with "venues" (places to have fun), businesses with patrons. Additionally, each building also either produces or requires one of more of the "values" -- productivity, prosperity, creativity, spirituality, authority, and knowledge. If you build a Liberal Arts College, for instance, without the requisite combination of creativity and knowledge, the building will not function (and you'll get something like a no-power zot flashing above it). By building objects like decorative murals, playgrounds, public libraries, and elementary schools, you can increase your creativity and knowledge scores sufficiently to support more and more buildings. As your total score for each value increases, more and more buildings are unlocked.
In some ways, I miss the ability to play around with the city-management aspect of the older games. Societies is less a city simulator and more of an anthropological experiment. My advice: consider the game on its own merits, and don't buy it simply because it shares a name with a series you like. Conversely, if you've never played a Sim City game before, but think you'd like this kind of social experiment, don't hesitate to pick it up. It's a solid game that stands on its own merits, but if you expect it to be like a more advanced version of Sim City 4, you're going to be disappointed.