Solutions like this have been around for awhile. A bunch of different companies make them. Chances are, unless you have a TON of SPS
corals or something eating away at a lot of your trace elements, you really don't need to be worried about dosing. PWCs will take care of keeping your levels in check for most tanks.
As for general opinions on it, I wouldnt know. I have never really dosed a two part solution. I know there is a really good write up on dosing 2 part, and how to make the solutions yourself. If I ever had to dose, I would DIY for cost, and you know for sure what you are putting in your tank.