I've been looking forward to this one. I first enjoyed Graham Annable's Puzzle Agent last summer actually on the iPhone, even though it was also released for the Mac and PC previously. The sequel is now available on iOS, and I can't wait to play it. Annable's weird mix of homespun comedy and creepy gnomes is fascinating to me (and you'll love it too, especially if you have a taste for the weird and slightly frightening), and Puzzle Agent's puzzles were ingenious little bite-sized affairs, paced perfectly well with a story full of wacky characters and twists.
There's no Game Center integration here, and the presentation might not be perfect -- the first iPhone title suffered a little from weird graphical glitches (though there were no game-breaking bugs that I found). But nevertheless, the Puzzle Agent series is much-loved by a certain crowd, myself definitely included. If you know you'll like it already, you can pick it up on the iPhone for US$4.99 or on the iPad in HD for $6.99. If you've never played the series before, you can check out the first title for the same prices, play through the free version, or just wait a bit for them to go on sale.