This post was super helpful for me. Thank you for it. As I recall, there is some similar information given in the pinned post at the beginning of this thread, but when I followed the directions there, it didn't work for me and I eventually gave up. I think I probably failed to add the leading / when I changed the paths to /mnt/... If it's possible to put a link to these better instructions from TheoS53 at the first post, that would be a good idea.
But it's still not all candies and unicorns. Because the first two times that I followed the 15-step plan laid out in post 5960, it didn't work. I think I figured out why.
First off, it seems that no matter what filename you give the playlist, when you reach the step where you instruct the DX80 to import it, the device renames it to something like "Playlist1" and there's nothing you can do to change that. Annoyingly, it also creates an empty playlist with the name that you chose (which if you're not paying close attention means you may not realize that you actually succeeded in importing a playlist to the DX80). I created a test playlist called "Popular.m3u," copied it to the DX80, rescanned both cards, located and imported Popular.m3u, the DX80 did a quick scan. Now I have an empty playlist called "Popular" in my Playlists list, and the songs that I listed in "Popular.m3u" show up in "Playlist1." I haven't yet tried to make a second playlist; I hope that doing so doesn't overwrite Playlist1.
EDIT: NONE OF THIS ACTUALLY WORKS... READ BELOW
Second, I made my test playlist using Banshee, which automatically (and unnecessarily) adds # comments for each song in the exported playlist. I think those # comments confuse the DX80. I am not 100% sure of this, since the bug with renaming the playlist meant that I didn't actually look at Playlist1 the first two times I ran my test. But given what I know about how kludgy the DX80 firmware is, I would not be in any way surprised if it is not capable of dealing with comments. I'm sick of messing with this tonight, but if I'm feeling charitable later this week, I may troubleshoot further and confirm/deny that # comments mess things up. Suffice to say, though, that it can't hurt to delete them when you're editing the playlist.
Finally, I'd just like to make it clear that I find it a tremendous burden that the DX80 can't parse paths sensibly in imported m3u files--that this only works if you jack around with a text editor and tweak things manually. This is not hard. People who want to import playlists don't care if it takes a couple more seconds for the device to find the songs if the alternative is jumping through hoops in a text editor. As I've said before in this thread, I understand the need in our current tech landscape to release functional (if buggy) software and eventually get around to fixing it. But if you never get around to fixing it, people will stop buying your products.