Some issues I've found with v4.55
F.lux v4.55 messes with putting my computer to sleep. I found that my pc doesn't fully sleep when F.lux is active.
Another issue I found was that each time I exited the program, it would forget my location. All three times I've exited F.lux, each time I reopened the program I'd have to reset my location.
There may be more issues, but these were the ones I found most crucial and could remember off the top of my head.