Yeah, there are currently a ton of great ebook apps like Kindle and other ones for viewing documents like PDFs, and I'm sure an iPad optimised version is coming soon from the majority of them. I don't think we need to worry about iBooks DRM. The only real problem is the software/app issue in my opinion, but jailbreaking somewhat solves that for people tech-savvy enough to do it.
Stanza is great, there is also GoodReader for PDF's, Wattpad, Amazon's Kindle app and the Barnes and Noble reader among others. Some of them have their own DRM, but there is definitely still choice.
