I recently bought Puzzle Agent for my iPod touch 3G, and was dismayed to find that it ran very choppily and crashed after about 5 minutes of playtime, before even getting to the first save point. I'm not sure if anyone else has experienced this or just me, but I thought I'd post about it just in case.
I was able to solve my problem though: after restarting the iPod, and making sure I had no other apps running at the time (I'm using iOS 4), it ran perfectly smoothly with no troubles at all.
So, in short, if you're having trouble with Puzzle Agent running smoothly, just make sure you quit all your other apps before you run it. I'm guessing it's an issue of having enough memory to run, probably.
Not sure if this belongs in Game Support or here in the Puzzle Agent forums, but feel free to move it wherever it fits best. I'm enjoying the game so far, love the atmosphere it has, and it feels like a good fit for the iPhone/iPod touch. Hoping Telltale will consider bringing more of its games to the platform in the future!