I tried Reaper before I got the iPad and got... Nowhere! The complexity of setting it all up with an external sound card defeated me. Several days at it with one lousy guitar track to show for it sent me straight to eBay with the gear and saving up for the iPad.
Willing to give it another go - surely there's less to go wrong just plugging in a midi to USB cable, and my new laptop is more powerful... The price of EZ Drummer is amazing too, so I'll give it a go. It's a shame it won't record straight to a set of audio files I can Dropbox into Auria, but the program itself looks spot on, so should be worth the effort.