If it had occurred to me, I'd've checked for the MP3 resume thing beforehand. An example of how even a lot of research on a device can still miss stuff.
I was looking primarily for something to play audible.com files a the time, and wanted to avoid iPods for a variety of reasons (one of them being simple stubbornness
). With Audible files, the playing software does the bookmarking automagically, it's one of the features of audible books ... and probably one of the reasons it didn't occur to me to look for bookmarking in MP3 files. (sigh)
I'll have a look at Rockbox, and see if there's any chance of it working on my player.