I do spray my prints, mostly for protecting the surface of the paper during handling. I seem to have a love for papers with delicate surfaces, and since I use flat print storage drawers, even with interleaves I've had handling cause surface damage to un-sprayed prints. I also love how the spray gives a last little pop to colors and blacks - I re-did my soft proofing profiles so that I take the impact of the spray into account. I spray whether putting a print under glass or plexi or not. In my own house and studio, I display without glass, but I haven't had a buyer yet who didn't use glass or plexi.
I use the Desert Varnish/Hahnemuhle/Premiere Art sprays pretty much interchangeably. I hate the toxic smells, even in a large bathroom with two large industrial cooking fans for venting, the smell travels everywhere.
I have had miserable experiences with the Krylon sprays. They're a lot more likely to puddle, run, and I had visible (and audible) variations in spray output when using. After trashing a few prints that cost $125 just for the paper alone (huge panoramas) the Krylon is never allowed to cross my threshold again.
I'd love to move to the more eco-friendly coatings, but every time I read "brush on or roll on" I shiver with fear. I can't help but imagine risks.