After having owned the JBL for four days, here are my short-term impressions:
Pros- Great value-- generally half the price or less of other 5" e-readers
- Lack of black screen between page turns
- Support for an insane amount of formats
- Good language support
- Location of place in each book saved, even if you read a dozen other books afterward
- Built-in dictionary
- Reasonable book load times for internal memory
- Outstanding screen performance in sunny environments and also in dimly lighted places
- Multiple ways to turn page
- Ability to rotate page-- good for pdfs that have wide lines
- TXT file reflow support
- Fits in my pocket!
Cons- Slow loading of books off SD card (benched at supporting 15MB/sec)-- likely culprit being the JBL SD reader
- Large ebooks take forever to load, and 1MB is already large to the reader
- Weird screen flicker problem (click for link to problem)
- No PDF reflow support
- Choice of only 2 fonts-- can't add own
Overall the JBL is an excellent reader unless you plan on using PDFs that you haven't formatted to fit the 5" screen and try to read large volumes without splitting them up beforehand. Using the plain-text format(TXT) works the best for me with dictionary support, reflow, and fast loading. Not all ebooks, especially those with DRM or pictures, can be converted to TXT though. Also my 16GB SD card with fast read times is hampered by the built-in SD reader on the JBL.
I bought the JBL as a stopgap reader to tide me over until the next-gen large screen readers come out later this year and early next year. For what the JBL promises to do, it does well and at a very compelling price. For those that don't want a kitchen sink, are tech-savvy, and want a reader that can fit in a pocket (even the jeans of a thin guy like me), I would highly recommend the JBL.
Click to view pictures of JBL and a comparison of its size with a phone and index cards: