I have the 680 and its been a solid, good sounding unit. I've had no complaints regarding it's sound quality and in several cases have been very happily surprised by what I'm getting from it. I'm feeding it with 2 sony diversity wireless units, soon to be 4, so it's valuable to have 6 inputs (4 xlrs)
Usage wise, there's a made-for-680 portabrace bag which is great and provides easy access to all parts of the recorder whilst in use. I wish the same could be said for some of the control/menu/ergonomic choices on the unit itself. For some obscure reason there are 2 separate menu functions, one of which is accessed via the top of the unit, which would typically be covered. It's a peeve rather than a deal-breaker, for me, as once setup you don't really need to frequent that part of the recorder too much.
I'm currently exploring timecode options, so far I've narrowed it down to an Ambient Lockit box, which I'll jam-sync the Scarlet with. Apparently you can take a feed from the lockit and record it to channel 6 of the tascam. In post you can use WaveToBWF to convert the audio-recorded timecode to a bona fide timecode track.
There's some good information here:
and the wave to bwf tool can be downloaded as a demo from here: