Yes DRM is a big issue, because not all devices support all formats. The only DRM format the iPhone supports is eReader, but no current Eink device supports that format. DRM is how they enforce kindle-exclusive books. (While I don't mind Amazon being the sole seller of a specific title - at least for a limited period - I get extremely furious about the limitations to what I can read the books on.)
DRM is like saying you can only watch movies on a TV you bought at Target, not one you bought at Wal-Mart; or if you want to read our book you have to use our glasses.
I think it's disgusting.