I personally went this route because vodka and vinegar dosing seemed more complicated...NO3PO4-X gives a baseline dosage based on your nitrate levels, tells you to test once a week, and adjust when / if needed. (Plus I had bought a bottle of it a while back when I was dabbling with the different methods of carbon dosing so I figured I might as well use it up as it hadn't expired yet.)
I had a bio-pellet reactor (undersized for my 266G build though) and could never get it working well...Most likely just wasn't patient enough and I added it to a system that had been running for almost 2 years. Other thing I noticed was the Cyano that showed up and it never really went away until I took the reactor offline.
I also figured that if I was vodka dosing it'd more or less end up in a mixed drink of sorts. Why waste booze!?!

(It's cold here in MN. Got to stay warm somehow!)
I personally don't think NO3

o4-X is any better than the other options, probably slightly more expensive than vodka dosing and definitely more expensive than vinegar (I assume)...I'd like to try pellets again, but the reactor I'm looking at just isn't in the budget at the moment. I figure that the cost is about $20-25 for almost 2 months worth of dosing and it seems to be working right now, so might as well not change it.