1) Nope.
2) Honestly mine seems to freeze up periodically when I add a ton of music (maybe once every two months or so), and it's a pain in the ass to wait for the battery to drain before it'll reboot itself. I haven't seen any way to reset it in the software either. That said, I had my previous player - an iPod - freeze up periodically too. Not the biggest of my concerns.
3) Like rms said, there's the letter shortcut, but you can also hold the up/down buttons down to scroll faster, and you can hit up at the top of the list to jump to the bottom of the list.
4) Not sure. I recently tried some .m4a files on it that I'd ripped and they didn't work, which was a little irritating, but the documentation says m4a is supported, so maybe I ripped them wrong. I suspect rms is lying about "any audio" being supported, because online it lists "MP3, WMA, AAC4 (.m4A), WAV (ADPCM), Audible 2,3,4" as the supported formats.
So yeah, good questions to ask.
I still like it better than my last iPod though.