The Sony PRS-T1 is the only active e-reader the company is marketing and has suspended production on all previous models. Since this is their new flagship model they tend to update it more then other companies. A new firmware update 1.0.04 was just released and promises a number of enhancements. Below is the the official log of the new fixes to go into the e-reader. Please note that the update is over 100 MB, so make sure you have enough room on your e-reader. You can download the entire update and step by step instructions via Sony Support.
Improvements over system software version 1.0.03.11140
•Resolves an issue where using a very short page flick to turn a page may accidentally select words and start the dictionary lookup
•Improves touch panel functionality
•Improves stability when searching the dictionary
•Improves Internet connectivity
•Improves Digital Rights Management (DRM) contents compatibility
•Resolves an issue where the Reader is unable to download some e-book files