adz: judging from my previous model as well as the new one, what you're seeing is perfectly normal. If the drive is 32GB, where exactly do you think the OS is supposed to reside? I too am seeing 28GB available, so the OS is taking up 4GB.
As J.Fo said, the new apps will be slightly bigger and the OS artwork is bigger, etc. ISTR that the iPad 1 took up maybe just a bit less space than this one.