The F6 is a great recorder for the price. The features are many, but it lacks in some fields: the slope signal that can be used for syncing in post can't be automated. It's there, but I can't go in a submenu every time I have to record audio that has to be synced in post. I know it has Timecode, but I can't use it without buying other expensive gear to use with my prosumer camera. Even the Tascam Dr100MkIII has this feature that solves so many quirks and problems that I couldn't justify the fact that is a thing is there but is unusable because can't be automated. The line out can produce an audible hiss in cameras that doesn't support line level input. The only workaround is to use a 35db attenuator cable that is really hard to find in online stores.
Overall the great feature of this recorder is a little obscured by its faults, but is a good starting point to do better in the future, maybe an H6 version of this, more portable, with an automated slope signal and an attenuable line out for prosumer cameras will be a no brainer, an instant best of.