Thank you! I have an X5L 20GB on the way. Should have it tomorrow.
I'll hear if it sounds better than the iPod (I understand it does) or an iRiver IMP-550.
EDIT:
The X5L arrived yesterday it is in beautiful condition, with charger and the connection subpack. Tested for functionality then Rockbox'ed !
Construction: nicely made, I appreciate the metal construction. It feels solid. To protect the headphone jack one should probably use right angle headphones or purchase a small right angle adapter. Being on the left side quite a bit of leverage could be accidentally placed on the jack.
LCD quality: As many have indicated: low resolution and the viewing angles are poor as viewed from above and below and fair from side to side. The brightness and contrast controls (which have a wider range than the original firmware) can help the overall viewing experience. The player doesn't appear to be made for video or picture viewing other than for very casual use. Having the ability to create themes really helps mitigate the shortcomings of the LCD. The Elephant's Dream video plays well (none of the 15fps limit from the OF) and motion is smooth.
Sound: This is what we came for and the X5L did not disappoint. In the original firmware flac files were *almost* gapless, for vorbis files the gap was quite noticeable. In Rockbox -- both truly gapless of course. The sound is brilliant. Sufficient power to drive Sony MDR-EX500, Sennheiser PX-100 extremely well with authority. Lows are solid and highs are clear. No fear with boosting the bass on this player -- it can dish it out. That's what seems to be the separation point: players that sound good and balanced (even when loud) but thin with no authority and players that sound as if they could be played and adjusted as one desires without fear of distortion or wimping out. The iPod doesn't really have this "authoritative" quality, the iriver IMP-550 (cd player) does and so does the Cowon X5L.
Controls: A bit quirky with the joystick, play/pause and menu buttons separated using with original firmware and that quality doesn't change with Rockbox firmware. Still, it's only a small learning curve and becomes second nature in no time. Changing tracks seems a bit slow with FLAC files but it seemed a bit slow with the OF as well.
What does one lose with the Rockbox upgrade? Not much: The (mostly) annoying sonic effects, replaced with Rockbox's own better (IMHO) effects.
What does one gain? Album Art, removing the 10000 file limit!!!, simple bass and treble controls, customized interface, additional CODECs, somewhat better file navigation (IMHO), database, games, full motion video and all of the typical Rockbox advantages.
The 3.7.1 firmware reverts to the Cowon USB functions when USB is attached and Cowon's battery charging when done so with the jack subpack.
The X5L is getting rather old and existing samples for sale increasingly seem to be showing the wear and tear of use (put them in a case!). Even so, there are good, excellent appearance ones to be found. If one is looking for, primarily, an audio player with a few nice things added in, the X5L is great and Rockbox makes it even better.
Thank goodness 1.8" SSD are 5mm in height -- though not cheap they should fit into the X5L just fine. The Toshiba 240GB HDD is 8mm in height and is *technically* too large. I do have an old 40GB 5mm 1.8" drive.
I'll update as the experience continues.