Termophilus
New Head-Fier
I know which feature you're speaking of - I use it on my Rockboxed iPod Classic for podcasts and whatnot.
And yes, Rockbox on th X3 can do this. While playing, hold down the play button, then scroll through the list to "Pitch". It's at the very bottom of the list, so it's fastest to just scroll up 1 option, which will bring you to Pitch. In other words, hold down Play while playing, scroll up 1 and you're right there.
That's good, but you confirm you can change only the pitch, and consequently the speed, not the two parameters separately? Changing speed without altering the pitch is the best option obviously, let me know!