This would be the ideal situation for me. Is it legal and easy to do?
I'm not sure about legal. It would seem analogous to making a backup copy of your DVD, but as far as I know, it hasn't been tested in court yet whether removing DRM for personal use is "legal" or not.
Easy? It takes a bit of work to set up the de-DRM program. Once it's set up, removing the DRM is a few clicks. Converting to ePub is easy through Calibre. Still, it's a lot more work than just downloading a book and start reading. I do it because I like the font in iBooks, and I like being able to copy and paste passages from the books (can't copy from a DRMed book).
For more info, see the stickied threads here:
http://stream-recorder.com/forum/removing-drm-protection-ebooks-f63.html?
If only the Kindle weren't so fragile... It won't survive a drop like the iPad does.
My local library (and it's quite common now) lends eBooks in the ePub format so I mostly use iBook or Stanza. That said I've never bought and eBook from the iBook store or Kindle Store.
Entirely Kindle. At the moment, the selection in the Kindle store dwarfs what's available in the iBooks store. That's the deciding factor for me. It's also nice to know that Amazon is not tied to any one platform. My books are still available in the unlikely and unthinkable event that I happen to pick up an Android or WebOS tablet at some point in the distant future.
100% Kindle (it's an e-ink thing)
I think the OP meant the Kindle app on the iPad, not the Kindle device itself
Kindle. If I'm going to be locked into a store then I want the one with the most books and the most device options.