I used a reactor on my last tank. One of my goals in setting up this tank was "keeping things simple" - mainteance and equipment. This was why I went B-Ionic.
I dosed it by hand every morning before work. I was pretty good at remembering, too! I didn't want to buy and dosing pumps for it, as that didn't fit my goals.
But, my wife and I like to vacation often, and i started wondering who would dose this while I was gone. My best friend lives 5 minutes away from me, and he always babysits my fish, but he's not a reefer. He can feed the fish, but I didn't want to worry about him dosing the 2-part...thus, back to a calcium reactor.
I can say this piece of equipment sure makes life easy. It really is a set and forget piece of equipment.