I personally have a 1.5GHz 12" PowerBook G4 (the last model they have). They do suffer from a few problems, like one where one of the memory slots going bad, or the problem with it going to sleep for no reason. There are also problems with the display, and like all the PowerBooks and MacBook Pros that had the same design suffer from dents because of the soft aluminum.

My PowerBook 12" leaves a little to be desired in terms of speed, but if your upgrading from a Pismo, it should be a big increase in performance. All the last PowerPC Macs are stuck with 10.5.8 Leopard and iTunes version 10.6.3, which seems to be the minimum requirements for syncing your iPad, according to Apple's website. BUT, thats running its original firmware. I don't know about iOS 6, but I know that iOS 7 requires iTunes 11.1 to sync, which requires 10.6.8 and an Intel processor.