I usually skip a generation with hardware and the iPad was no exception. I limped my original iPad 1 along all during the iPad 2 years and finally bought a replacement the iPad (sort of 3). My biggest use for the iPad is music making so the incredible retina screen is 2nd on my list of features. The biggest bump for me musically was the processor speed. I believe this is near the same speed as the iPad 2 but from the iPad 1, the change is very welcome.
Garageband is now a pleasure to use since it isn't constantly mixing down the tracks to conserve memory. I've also finally rediscovered Retronyms Tabletop which really didn't run at all well on the original iPad. Tabletop is pretty much a Reason knock-off for the iPad and is a very good "virtual studio" approach although it does nickel and dime you to death with in app purchases.
Something about it must be appealing because I keep trying it out. I'll probably get a song out of it shortly and I do love that every knob and button can be recorded.
Another recent accomplishment, I finally put out a small piece with Sunvox. This is an old-school tracker with very odd user interface but I am impressed by how powerful it is. If you have the patience, you can pull off almost anything with this tool. It includes a very modular synthesizer and runs on every platform imaginable. Its easy to move your work from device to device. I must say that the iPad interface is a bit cumbersome - it was sort of made for either stylus or mouse use but it does work.
Here's my recent effort with it:
My other favorites also work more or less unchanged with the new iPad. I've been working quite a bit with Garageband now that it supports note editing and is almost a complete DAW!