I never owned an iPhone or iPod touch so the whole apps thing is pretty new to me.. So far any apps that I've purchased or dl'd were from iTunes.. Are there other places to get iPad apps or just iTunes for now?
It's easy and seamless and any app your buy (or get free) downloads immediately. Just be sure to connect to a computer via usb from time to time and pick "transfer purchases" in iTunes to back up your applications. I didn't do this and I lost a lot of apps when my iPod crashed. Sure, I could download them again 1 by 1, but the only facility Apple provides for getting your apps back after a crash is usb + iTunes.