What everyone else said...
I myself have gotten the price of the software in entertainment alone. Of course, not everyone is entertained by such things as playing "What If?" with different powders and calibers. Keep in mind, It'll be 7 months until comfortable shooting weather comes around again up here, so you look for things to entertain yourself.
Ever wonder "Why not H4895 or CFE223 in my 450b? QL answers those and many more at the click of a drop-down box. "What if I seat that bullet to 2.26 COL instead of 2.10?" One thing it has yet to include, is what the different primers do for a load. That one is left up to you to discover through range visits.
Its not hard to use and you can delve as deep into the fine points as you choose. It does err on the side of caution as I suspect that the author does not want to rely too heavily upon every person using it, exercising good judgement. I've used countless loads across 5 calibers with it and they always come in lower in velocity and presumably lower in pressure also since one contributes to the other. I don't have 5 pressure barrels for testing so I take that latter statement on faith. That conservative approach is not a bad thing as once you calibrate your result to what was predicted, you can tweak some of the parameters to get the predicted result darn close, as BW460 said.
Hoot