frblckstr:No, and in my view it doesn't need to, the lit format is working the best for me accross PocketPC, TabletPC and PC (and now the UMPC).
The biggest problem I have with the current ebook formats is that they are closed, DRM-based formats. I'd love to try the new UMPC-optimized MS Reader application, but I already own a pretty large collection of ebooks in the eReader format. In addition, MS Reader is such a closed format that it only works on MS operating systems, meaning that if I started using their format going forward then I wouldn't be able to read the books on my Palm OS based Treo...
This, of course, is just a variation of the same DRM nonsense that is going on with music and video as well. Ultimately, I don't think digital media is ever going to really overtake its non-digital counterparts until the industries finally come up with some standards that ensure interchangability. This is the kind of stuff that the general public shouldn't even have to think about...
-Jeff