1000 song limit (per list). This is work-aroundable, but a pain if you want a super-huge shuffle set.
Touchy reset. It is easier to reset the Express than to shut it off. To reset, hold select and volume+. You can do this by accident just by picking it up. Why not take 5 or 10 or more seconds delay, making a button-mash accidental reset hard to do?
Volume lowered on power-down (I know, safety issue, but the Clip doesn’t do it). If I want to listen to it loud (and in my case, hook it to an FM transmitter that wants high volume), why should I have to mess around each time I turn it on?
Slow scroll though song/artist/etc lists. About one minute per 100 entries. With enough songs, it can take more than the length of a song to find your next pick.
Not-really random shuffle. Reset will give the exact same shuffle order every time, and shut off may do the same.
No MSC mode from Menu Option (again, Clip does it).
Touchy handling of poorly/non-tagged files, can end up with “phantom” entries. Sadly, if you get these a format may be the only fix.
Not exactly a firmware thing, but the manual doesn’t cover the recovery mode (hold volume- when connecting to PC), and details for off-line (and non-PC) firmware updating & restoration aren’t in one easy to fine place.
The Express has two big things which make up for a lot: direct USB connect (no cable needed when you travel/visit), and the memory card slot. Its sound quality is fine, size and battery life are good, price is nice.
A firmware fix for the worst glitches would be a great way to gain Sansa fans.