Mine was definitely one the 200 series SanDisks! I can't say for certain which device I used. I got the device from my roommate, who got it in a woot.com "bag of crap" that included a couple refurbed mp3 players.
I remember the default firmware being extremely slow to use. It spent cpu time it couldn't afford to render animations between "apps" that added nothing. I think it may have been extensor picky about which codecs it supported, though I wouldn't have had much that wasn't mp3s.
I really loved rockbox. I liked how configurable it was, and how minimal it was. I'd previously used sdd based mp3 players. A dell dj (I was crushed when they canceled that line, and more so when the Seagate hard drive failed) and the first gen video ipod.
Rockbox worked very well for music, which is all I used it for. I always used windows explorer to transfer files to /from, and that worked well.
I found installing rockbox very easy. More so than installing ddwrt or homebrew on a wii. I don't think I ever updated rockbox. I probably used it for a year and a half, max.
I only stopped using it when I got a smart phone. I would certainly still be using it today.