I love reading books on both my Pocket PC and the Sony U-70, but I usually do my reading on the Pocket PC. It is just more convenient due to its small size and light weight. I have been reading ebooks almost exclusively for several years and can’t remember the last book made from dead trees I have read with the exception of a very few technical books not available in electronic versions. My reader of choice on both platforms is eReader, formerly the Palm Reader. I love the simple interface and I especially love the unobtrusive DRM the ereader.com uses.
Another good site for purchasing ebooks is Fictionwise where I shop from time to time but recently I discovered another source for ebooks that I really like. Diesel ebooks has a selection of over 35,000 ebooks and the web site is very clean and simple to navigate. All books are categorized in an intelligent method and their web site is just a joy to use. Diesel offers ebooks in three different formats: MS Reader, Adobe Reader, and Palm eReader format. Diesel also has a HUGE selection of free ebooks from public domain works so if you are interested in the classics you won’t be disappointed.