I also use muriatic acid. All the time! I actually use it to a 4:1 ratio with water and just run the pump in the acid. I've forgotten about pumps before, and left them running in there for over a week, and there was never a problem. After they run in the muriatic acid for a while, I manually wipe them down in the sink, then run them in clean water for a bit. I've never had any issues, either.
Vinegar is... <checks online price> ... about $15/gallon, and you have to mix 1:1 for even partial effectiveness. Muriatic acid is $7 for 2 gallons at Home Depot (pool aisle outdoors) and you can mix it as weak as 20:1, as mentioned. MA has to be done outdoors (I just leave it in the garage), but vinegar stinks up the whole house.
I put powerheads, float valves, heaters, you name it, in the MA:water mix.