I've been using it for a while now. It is an excellent tool in the tool belt, making me a much better developer and more productive, a lot less messing around.
I'm using it all the time as my main development browser.
It's been awesome using it. It's not just responsive design, it has fantastic features around accessibility and performance, I can set different viewports to different speeds and colour contrasts all at the same time. It is bonkers how powerful it is as a tool. I always recommend it to people to try out.
It doesn't put me off, but makes me more cautious. I need to put more effort and focus on what makes my product different to the competition.
That clarity can really help push your product forward in a crowded market. I also feel that doing 1 thing and doing it well or better at launch can really help.