Be careful - currently available Sansa Clip Jam and Sansa Clip Sport are not supported by Rockbox firmware. Supported versions are Sansa Clip+ and Sansa Clip Zip (and some even older models).

Killer feature of Rockbox for me is possibility to change playback speed while maintaining original pitch. As most audiobooks and podcasts I prefer to listen on 120-130% speed.

Most recent Sansa Clip models dont support Rockbox iirc, you'll probably want a refurbished Clip+ or something like that.

Automatic bookmarks, which is very useful for podcasts. The file automatically continues where you left off last time. Oh, and you can also play DOOM on it of course!

And Pac-Man.[1] And Tetris.[2] And Mario.[3] And if you're particularly masochistic, The Hitchhiker's Guide to the Galaxy.[4,5]

And loads of other games and programs.[6]

1 https://www.rockbox.org/wiki/PluginPacbox

2 https://www.rockbox.org/wiki/PluginRockblox

3 https://www.rockbox.org/wiki/PluginRockboy

4 https://www.rockbox.org/wiki/PluginFrotz

5 https://if.illuminion.de/infocom.html

6 https://www.rockbox.org/wiki/PluginIndex

The original firmware also supports resuming from the last played position in podcasts and audiobooks. Whenever you select a partially listened item, you get a prompt to continue from the last point or start from the beginning. It's really handy and honestly I couldn't live without it.

There's a simple binary database in the root folder that keeps this information, but it gets reset whenever you add/remove files. Now that I think about it, it might even be possible to backup that info and restore it afterwards, although I never really needed to do that. I don't usually have more than a couple books/podcasts in progress, so it's easy to remember where I left off, if needed.