Everything went smoothly: from the moment I was contacted through Thumbtack until I said 'Thanks, man. Enjoy the rest of your weekend'.
Up front the cost was mentioned, there was a contract and I was called to make sure everything was good. There was a weekend charge that was made very clear and even followed up on to make sure that I was aware that was a thing, which is totally fine and I'm glad it was made very clear that that fee was going to happen.
The tech was available a bit earlier than scheduled so they had called to ask if that was cool. It was. So they got started early. I pointed out the problem and he immediately got to work. Turns out there was some gunk buildup in the iron pipes (it happens) and he removed it. Even said he would cut the pvc pipe leading into it to help mitigate the problem from happening in the future. No additional charge for that. Of course I'll take that.
All-in-all, I would highly recommend. Very professional, very prompt, and left the area in a clean state. The guy does everything too: HVAC, electrical, plumbing. I am keeping his card for future work.