My experience has been good. For about an year I worked full time. And then later on, because of wanting to work on my own projects, switched to part time.
But, of course, any platform is not perfect, and mileage varies. One of the problems, I have seen other people face and say is difficulty in getting the first client. But in some of those cases, I also found, that their experience was in a narrow domain (e.g. Wordpress developer in one case). If a person is skilled in a breadth of technologies, then I think, its relatively easier to bag a client.
Also another valid criticism of it is, the selection process is very tedious. Personally, I like solving algorithmic problems (and had spent time learning and solving DP/etc based problems), so I didn't have much issue at that stage++. But often several good developers, don't find that stage to be useful. And I agree, as some friends I referred, struggled with that, and those people I had worked in the same team for long, and know them to be very good developers.
But despite some issues, I still think, it has value. As for me, it solves the problem of being in India and work for SV client, and get good rates. Also no commute. And use that time for exercise instead. Also of late, the ability to work part time, and work on my own projects.
Ask me any other question you have, I will try to answer it in a generic way (not ready to reveal my specific instance details)
++ Edit: I too had difficulty at the mock project stage. Where I found it too cumbersome. Especially the UI part, in React, and was almost ready to give up. It was also partly due to over-committing at that stage, and promising them a demo in 10-12 days, as I was eager to finish the process fast. May be in hind sight I should have taken 16-18 days. As I was not fresh with Reach and was learning on the job (as we all sometimes do)