I've seen some discussion of this (or something similar) before, so apologies if this is 'one of those subjects'. I've had a little search, but couldn't find much recently... Here is an older thread for reference, anyway.
http://forums.rockbox.org/index.php?topic=11922.0I use my player (sansa clip+) exclusively to listen to podcasts, and for me a killer feature would be to lose concentration for a few moments, and be able to click one button to skip back a fixed amount. It seems some people want to skip forwards as well, or skip folders.
Obviously having access to all of these features at once is difficult from a UI perspective - unless you want to go down the fully configurable buttons route, and it seems you don't.
I propose having a menu option that allows you to configure what tapping downwards (which would be the one you hold to get to playlists, assuming it's wired differently for different players...) does - say between nothing / skip back X seconds / skip forwards X seconds. Other options always possible later.
It's not ideal from a 'power user all options always available' perspective, but it doesn't alter / override the current UI in any significant way, and I (perhaps naively) suspect it wouldn't be that hard to code. I know featureitis is to be avoided, but this would *immensely* enhance the usability of this firmware for at least some users.
Thanks for reading... (P.S. it's already looking awesome on the Clip+! Congrats!)