At the risk of being flamed, I do use MAQS and have a lot of success with it. Occasionally it triggers supersedure, especially if the queen is a couple of years old and presumably producing less pheromone.
I like MAQS for several reasons. Its active ingredient is formic acid which is a natural organic acid and doesn't cause mite resistance. It doesn't build up in the wax. It can be used in summer with sealed brood and supers on as it doesn't taint honey. It's a one-shot treatment with immediately visible results on the varroa tray.
I have learnt it's very important to follow the instructions. Use it only on good sized colonies (at least 5 seams of bees) and make sure there's plenty of room above the brood box for the colony to spread out. No top ventilation, entrance block out, varroa tray in if you have a mesh floor (otherwise the heavy vapour just falls out without doing its work).
Bee Equipment have been selling MAQS very cheaply but say the supplier now refuses to deal with them. See
MAQS Statement.
Thornes sell it at £55 for a box of 10.