We're having other reno work done and it was recommended that we increase the insulation in our attic (because of new water pipe just above the dry wall to the shower, the insulation was lacking in the attic). House was built in mid '70s and it had what was probably the norm at the time (R12).
We opted to get it up to R50 (current recommendation). The work was done in about 2 hr with some insulation mess on the carpet in the bedroom when finished (this was blown-in cellulose insulation).
This mess was cleaned so thoroughly by the installer that I couldn't find one spec of insulation anywhere on the floor when he was finished.
It may be wishful thinking but it feels different already on the upper levels (it had always been 5-7o warmer in the summer with the a/c on and 5-7o cooler in the winter with the furnace on).
I'd recommend Kort if you live in their service area (Erin, Ontario). They arrived when they said they would and cleaned up before they left.