It plays a lot like Farmville, which is a gigantic Facebook game in which you grow crops and cultivate plants of all kinds. Ngmoco's version is slightly different, but only slightly: you're still laying down crops, waiting for them to grow (30 seconds for the cheapest and easiest crops, and up to days for the rarer and higher-level items), and then harvesting them for in-game currency that lets you grow more and build more, and so on. It's not strictly a competition (you don't track totals with friends or score points for what you grow), but the game is very social, with push messages notifying you when crops are done or when your friends have done something spectacular or worthwhile. There's a big focus on customization as well -- you can build things like mailboxes or signs that make your realm very different from anyone else's.
So where's the "premium"? Every time you grow or build something, there is a little button marked "mojo," and "mojo" is a type of magical in-game currency that can be used to speed up whatever you're growing. Mojo can be earned slowly in the game, but if you want to use a lot of it, you can pay real money via in-app purchase to get more. Thus, if you want to grow the game quickly and don't want to wait to earn more mojo, you can start putting real money in.
Ngmoco did say that they'd "learned" from their previous games, and that they wanted to make sure that even the free game was a full experience. But that mojo button was awfully big and purple, and combined with the fact that there were also in-game ads all over the build we saw (when we asked if there would be a way to turn them off, even with real money, we were told that they haven't decided yet), it certainly seems like Ngmoco will do their best to get you to invest in the game.
The other game they are showing off this week is called GodFinger, and if We Rule is based on Farmville, GodFinger is Farmville mixed with Pocket God. The game is centered around a planet that you can rotate around with your finger, and the planet is populated by "followers" that offer you, as a God, all sorts of prayers and wishes. Granting those wishes (like adding rain to crops or sunlight to people who need their day brightened) will grant you "awe," which is another currency that you can use to upgrade your planet however you see fit, by terraforming the ground or building various structures and upgrades.
GodFinger is also very social -- you can actually "assign" one of your friends on Plus+ to a certain follower (as in, you can name a follower after your friend Katie), and then we were told that your friend will get push notifications and even benefits in their game depending on what you do to them. For example, if your follower Katie asks for sunlight and you grant the wish, your friend Katie will get a message that you granted her virtual wish, and even get a bonus of some kind in her GodFinger games.
We didn't see ads on the game, but of course being as this is Ngmoco, there is a "freemium" plan in there. You can purchase "awe" with real money, and that will let you use your god powers even more per day than usual, kind of like Eliminate's energy currency. GodFinger definitely seemed like it was a little less "pushy" than We Rule, in terms of asking you to spend real money, but of course, if you're playing the real game, there will presumably come a time when the game will tell you to stop playing for the day or pay up. It's still in development, of course, so even Ngmoco isn't 100% sure
Both games are definitely polished and well designed -- they ran great on the iPhone 3GS, and the graphics were colorful and easy to understand. But Ngmoco's main obstacle will be to keep their business plan from getting in the way of their game experiences. They say their main goal is making fun games, and it'll be up to these two games to prove it.