I'm coming late to this. I've been through two take-home projects. Both of them resulted in a no-hire, and each has refined what I'm willing to do and what I'm not willing to do.
The first one was a pretty egregious experience, honestly. I never spoke with anyone other than a recruiter. The first was a 2 hour Java test. The next was a take-home that I was supposed to spend 5-7 hours on. I did it and sent it in. I knew it wasn't great, but I put a hard stop at 7 hours. It took almost a month for me to hear back, from the recruiter, "we've decided not to continue with your application at this time..."
For a while, I said never again. However, after refusing (and passing on what might have been good opportunities), I did another. Circumstances were very different. I had two extensive interviews with developers prior to the take-home, and I was interested in the job. Furthermore, they did reply with feedback, though it was through a recruiter.
The feedback was mixed, some things were good, others were bad. Unfortunately, though, it was a hard stop. I didn't get and presumably will never get a chance to defend my choices. Although I understand the company probably doesn't want to open up a debate, they've moved on, it rankles that someone got to say those things about my code and I never got a chance to reply.
So, am I at the point where I'd never do it again? Almost. I think I would insist on an opportunity to defend my code base, at least one back and forth, before calling it quits.
It sounds like this company (mattermark) does this, which is a positive thing. You do get a chance to argue (though maybe they do cut some people off when the project is terrible, and who knows, maybe the people who rejected mine (no connection to mattermark) were just taking it a little easy on me, but were genuinely not interested after seeing it).
I don't actually care about getting paid for the project time, if it's a good opportunity. I have to spend as much time re-studying my data structures and algorithms book for whiteboard interviews anyway, and I actually my learn something from the take-home.
I'll probably talk to a buddy I consider to be a really good programmer who works in this area, and see what his take is on my project, asking him to be pretty brutally honest about his assessment.