A couple of things I've noticed that could be added/fixed...
1. Lack of Artist -> Album view. That way, scrolling through artists would be smooth, and the albums by that artist could have their art displayed (the most albums/singles I have by one artist is around 20, and I could stand the slower performance on that small list more than a list of 1000 albums). This is also generally my preferred way to browse music.
2. A paused file automatically resumes playing as soon as a jack is plugged into the line out port. I ever want a song I've paused to resume playing until I'm ready.
3. Somewhat related to the point above, I'd also prefer it if there was at least an option to stop the DX50 from playing files automatically after pressing the 'Previous Track' button.
4. A way to force the DX50 to scan the Card, OTG etc. I've experienced a very annoying glitch where the scan stops prematurely, and hasn't actually completed the scan. The only way to force a scan is by restarting, or connecting it to a computer while turned on. Adding this as an option would just be helpful.
5. Playlists/Favourites Playlist. The Cowon J3 didn't have great playlist support, but it did have a 'Favourites' section. This was particularly helpful when I wanted to just add my favourite tracks and listen to them in situations I couldn't safely change track. This is supposedly coming soon.
6. Battery charge indicator percentage. The lack of this feature has annoyed me on phones since the days of Symbian. A percentage is a much better visualisation of the level of charge. Shown in a photo previously released by iBasso.
7. An actual fix for the apostrophe problem. Some have reported that the apostrophe problem has been fixed, mine however has not been. I imagine that there may be several apostrophes in the codeset (for the life of me I can't remember what the standards for typefaces are, UTC or something. If anyone knows and could correct me I'd be grateful), and only one was fixed. Or, more likely, botched release.
8. The Gapless options should really be explained more. 'Close' clearly means 'Off', whereas the '5 sec' and '10 sec' options clearly activate it, but with seemingly no difference. Would be nice if iBasso (or anyone who knows, for that matter) could clarify this, as well as change 'Close' to 'Off'.
9. It would be nice to have some indication that something is actually happening on the 'Scanning Media' screen. Yesterday, after updating my DX50 to the latest firmware, I let it scan for 40 minutes and it had only reached 'Daft Punk'. How do I know it wasn't doing anything?:
10. After deleting the 'LOST.DIR' folder that the DX50 persists in creating, it scanned down to R in 8 minutes. One final scan completed it. Therefore, having a progress bar (or anything that indicates it is actually doing something) would be very beneficial for times where it can be doubtful. Not necessary for iBasso to include it, but would be reassuring. They could also try to fix the 'LOST.DIR' problem, since it does appear to be causing problems both with scanning and installing firmware.
11. Fix the Coaxial output to work with files above 24bit 48Khz.
12. Fix the slow playing 192Khz file problem (I don't actually have any 192Khz files to test this with, but others have mentioned it, so I thought I should include it, for the sake of being thorough).
And now for really nit-picky things:
13. A font with consistent kerning. I'll admit, this is pretty OCD, but looking at fonts where letters are unevenly spaced grinds my gears. Especially the amount that the DX50 does. Look at 'Internal storage' and 'SD Card' in the directory option. 'Internal' looks to be written as 'Intemal', and there is a large space between the 'c' and 'a' in 'card'.
14. Slightly less annoying to me than this is the fact that different letters have different thicknesses. Look at 'Now Playing' for an example. The 'w' is so thin on the right side it actually looks anemic. Interestingly, the left side of the 'w' looks normal', so I can only assume that a re-sizing error is the problem.
15. The font thickness problem also exists on the 'Home' page (where you can see the song playing). 'My Music' looks bolded after 'My M', with the capitalised Ms also suffering from anemia. 'Settings' is also noticeably thicker.
Added after editing:
16. A feature that automatically scans files added through USB, so that you no longer need to perform a manual scan (and also a way to turn this feature off).
17. Better error handling. The apostrophe problem was only discovered by experimentation with tags and filenames. It would be helpful if iBasso could add an error system that not only handles errors in a better way (i.e. not causing so many resets, frozen screens etc), but gives the user a notification or error screen/pop-up that tells them what has happened and why (if it's a technical problem like Windows' old BSODs, it would still give iBasso something to work with. All we have now is a rough idea how these errors are caused). If there had been a pop-up saying something like: 'Error: Could not play file due to invalid characters', that would be much more helpful than not playing the file AND not telling the user why.
Anyone got any other bugs to fix or features to add? I'm sure I will come up with some more, but for now I'll call this the 'abridged list of grievances'.
The three font issues are so minor in the scheme of things that I wouldn't care a lot if they didn't ever get fixed - on the proviso that the first 12 I mentioned were fixed/added.
EDIT: Forgot to mention that I had a glitch earlier today. I connected the DX50 to the computer, and was trying to delete the thumbs.db file that Windows automatically creates. I deleted it, and then the player became non-responsive to actions done on the computer (such as opening folders). I disconnected the DX50, turned it off and it turned on again automatically, repeating this every time I turned it off. Only a battery pull fixed it. This leads me to believe that it thinks it was still connected via USB, or handling a charging/power error incorrectly (hence why it turned itself on without me turning it on).
Number 17 could be an issue though, considering how buggy the firmware is at the moment.