I'd like to make one comment on the discussion about how best to transfer books to Marvin. I'm one of those eager folks who missed the beta test window and is desperately waiting for 1.2 for the OPDS integration.
1. Yes, Faterson is correct that you can accomplish many things without running iTunes at all. However, there are reasons why someone might still want to. For example, if you have a lot of ripped music (not purchased from Apple, for example), iTunes is really the only way you can transfer that music to your iDevice. If you're using iTunes for one thing, you might be inclined to use it for many.
2. I've found that OPDS is limited when you're dealing with big MB ebooks (typically reference or graphics-laden books). And yes, there are ePubs that can have many MB (I have one that's just under 100mb). In those instances, transferring over a cable makes things easier.
3. The cloud is great, until it isn't. The minute you've experienced a security breach with any of your cloud-stored data, you start to feel differently.
4. I would never recommend that someone who has removed the DRM from a book (even one they bought) store it in the cloud. That's tempting fate.
5. The only time I've used save to disk in Calibre is if I want to save it to an alternate location. Otherwise, I rely on the autosave feature that's been mentioned.