Ebrary, a digital library content distributor, is conducting apoll right now. They're working to develop new ways to support an offline/download model and to reading on handheld devices. They want to better understand your needs, and they would very much appreciate your comments and suggestions.
Update: This Survey is directed at librarians, and it asks questions that most of the general public may not be able to answer. I hadn't filled out the survey yet, so I didn't know. Sorry.
You can find the survey here.