As promised, here's a report of how my X02 flashed with the Agptek A02 firmware is behaving.
My Ruizu X02 is a white model, 8GB, bought on AliExpress. Seemed to be a genuine product, arrived in the original packaging with all the Ruizu seals, warranty (in Chinese, of course), manual (in English), and extras (micro USB cable, Ruizu-branded white earphones).
I flashed it with Agptek's Audio Product Tool, applying the latest v1.7 firmware for Agptek A02. I checked the FLASH_ERASE option to make the cleanest possible install. The flashing concluded without a hitch.
The A02 UI is cleaner and looks more professional. There's still some dodgy text formatting (alignment issues) and dubious spelling choices, but at least the menus doesn't look blatantly amateurish (like the Recor option in the original Ruizu firmware). I won't post screenshots. If someone's interested in the improved UI, just search for 'agptek a02' on Youtube and you'll see it. The only thing Ruizu got better was the splash screen. The A02 has a hideous pixelated low-res video which serves as intro/outro when you turn the player on/off.
The Settings menu includes a new option to set backlight intensity. I presume reducing this to the lowest setting (which still leaves the screen well visible) can squeeze out a little more battery life. As far as I'm aware, all other options are the same.
The navigation underwent an improvement, too. Now, UP (M button) is up, DOWN (Vol button) is down in menus, and LEFT & RIGHT are 'back' and 'special options' respectively. 'Back' means go back a folder, 'Special options' is in most cases only 'Delete'. While playing a track UP brings up the menu with playback options, and a short press on DOWN goes back in a folder without interrupting playback. To access the volume control a long press on DOWN is needed, after which UP and DOWN adjust the volume.
A novelty is the Easy Mode navigation. You activate it during playback, by a long press on the pause/play button. In easy mode folder navigation and accessing menus is disabled. UP and DOWN adjust the volume, and LEFT and RIGHT change tracks. Essentially, it leaves only the most necessary functions available and makes them easily accessible. To bring back Normal Mode, you have to press pause/play again.
The sound quality, of course, remained the same. The EQs still sound muffled to my ears, but that may be subjective. I just turn EQ off.
Battery life appears excellent as ever. I didn't get a chance to drain the player, but after more than 10hrs of listening to music, the battery indicator was still resting at full.
Note: I only tested MP3s. Haven't transferred any lossless audio yet.
The issues I encountered:
I outlined them in my previous post: track sorting appears completely random in Music view. In Folder view, playback doesn't stop after reaching an end of the current folder, but continues straight on with the next. After all folders and subfolders have been played, it goes right back to the beginning (Folder 1, Subfolder 1) and continues playing.
I tried removing the ID3v2 tag as suggested and replacing it with ID3v1, to no avail. Even after formatting the player and transferring files anew via the Copy In Order program, the sorting is still misbehaving.
Other functions I don't use, or need. I only quickly checked them for the purposes of this report: FM radio & recording and bookmarks seem to be working. I don't use playlists at all so can't comment on that.
Conclusion: To change or not to change firmware? I'd say, yes. The track sorting and playback issues were present in the original Ruizu X02. the A02's firmware didn't fix them, but has made overall improvements to the navigation and UI, so, in my case it was worth it.
