It has problems because it's a sophisticated software with lots of features at a very low cost, I have had problems with mini SD card, so I can't use use it, if it's not a high speed card.
In the beginning I had problems with OGG files but I solved it when I discover that OGG don't allow cover art embedded.
I also have a Meizu M3 which have take me lots of efforts and investigations to make it work as it should. This Meizu player have a very annoying problem when playing some kind of MP3, which it's not the case of ATJ2135 in none of the formats it manage. I hate problems with sound... and this haven't been solved by Meizu.
Teclast C260, other of my players, have started to have some bugs since they upgrade it to have the capability of managing of playlists.
My opinion is... when a software started to add functions, some problems arises...
I hope that support for your Ainol takes this in account and solve them... I sincerely doubt it. Only Meizu Teclast and Onda seems to have a team to deal with firmwares. I have heard that Cowon have it too.
That's why i love the simplicity of Rockchip... not much functions not much problems.
PS.: I am waiting for the proper firmwares of my player that the provider (Groven) promised to send me... next week I'll have to write them telling them that they have not fulfil the promise of send it to me this week.