Take a peek here for additionl info - I got tired of seeing this question so much I published an article about it.
Bottom line IMHO:
USO is the best thing going for a U.S. Shooter engaged in long range and ultra long range shooting. The business has had a checkered past, but this seems to have been fixed with a vengeance thanks to JWIII in the past few years. All of my guns now wear USO glass.
S&B makes a very nice product, but its insanely overpriced with current dollar vs. Euro exchange rates, and the diversity of their product line sucks comapred to USO. Given current exchange rates, you can get a SN-3 (provided its not the 40mm tube/88mm obj monster) cheaper than the S&B PM's. I picked up a lightly used 40mm/88mm monster for less than a used PMII - I was patient and looked hard for it, but it was a fantastic bargain and worth every cent. USO supports the shooting commmunity and offers great deals on their top of the line scopes at SH. No one else does anything even close to this.
NXS: Great scopes for the money - will handle almost all shooting situations well - biggest problem is they don't offer a front focal plane reticle.
Loopy: Best value out there if you are on a budget and are smart enough not to pay full retail prices for their stuff. Stay away from the luminated reticle models - they are still a work in progress.
As always, beauty and quality are in the eye of the beholder - I was just lucky enough to do a side-by-side comparison of these scopes for over a year in all kinds of varying conditions. In the end, USO made the best product hands down.
SCL in Bogota