Just finished 5 hours listening to 1.37. Had a scare, about the 5th song in the AK would not play, it froze. I forgot what the the display said. Powered down, turned back on and no problems thereafter. I listen on shuffle mode and the gap between songs still averages 4 seconds, this I never liked.
The sound, maybe its all in my head (hehehehe) I do hear what Ian talked about, crisper high, more space and better bass. Happy I updated.