Mine's downloading this very minute. :) You can read a review on CNet, but, I mean, it's Catan. You should just get it.
There are a growing number if board games making the jump over to the iPhone. As a development platform, it sort of mirrors the indie element of the current designer board gaming scene, because an independent designer can learn the ropes of iPhone development, submit an app, and almost instantly be selling it on the App Store.
There's a version of Werewolf designed by Kory Heath, as well as 3 Reiner Knizia apps - Poison, Robot Master, and Knights of Charlemagne. Poison is one I really like as a board game, so it'll be interesting to see how it makes the translation over to iPhone.