To be sure, there are the occasional rough edges on the FiiO, but whether you encounter them depends on how you use the device. I've had mine for months now and have had at most one crash (which I'm not sure was a crash, I may have been resting on things the wrong way and invoked the reboot menu, but let's say it w as a crash). So for people experiencing problems the sure, they may have a flaky device needing service, or may use the software in a way that genuinely crashes and would do so for every user who did the same.
Based only on my personal experience I'm having an awesome time with the device. Are there quirks, yes. The occasional glitch in playback timing or somehow-bluetooth-induced "pop" on my speakers sure.
I think my only real complaint is that navigating using the FiiO app in my 25k songs is _very slow_, depending on # of files in the directory, and perhaps sensitive to the way I have structured my albums. Whether there are corrective actions I might take I don't know. It isn't the card slot I've tried both. So my best guess is speed of the card, or simply the way I've organized my music.
Would I buy the device again? Yes, it fills a great cost/feature niche, sounds great, and is letting me enjoy my music in a way I haven't for decades.