I have been having image & video quality with mine as well. I have been biting my tongue though because I don't know how much is me vs the mavic.
One thing I have learned, as a few others here have stated, is that for stills, shooting in RAW is a must... otherwise, it is just complete crap. Even in RAW, I can't say that I'm impressed with the quality... but at least it is now tolerable for the most part.
Video for me has been really hit & miss. I often see strange artifacts and the watercolor effect too. It seems like some things that factor into this have been...
- Moving too fast while flying too close to the ground. It seems like the mavic (or maybe my settings) simply can't keep up with faster motion.
- As others have said, it seems like it doesn't do well in low light.
- I still struggle with the **** focusing. Yes, tap to focus... it's hard to explain... but it is really hit & miss for me.
All-in-all, I sometimes have beautiful video and sometimes it's *horrible* and I'm not always able to figure out why such a large quality gap. As for some of the artifacts and jerkiness I have witnessed, I'm hoping that ND filter will be the solution. I have those on order from DJI.... but it looks like they're not going to ship for a while.