I have a Sig 522 and a S&W 15-22. There was a question on an earlier Thread, that asked, "What was your Favorite .22 Rifle?" My answer, was that it was a solid tie, between by 522 and 15-22. I couldn't pick one over the other.
The 522 is a Solid Shooter, and very well built. It's the same size, and uses some of the same components, as the Sig 556. It's as easy to clean as my 15-22 AR style, as it breaks open like an AR with one pin, and the Upper can be removed from the Lower, by popping out a second pin. The Bolt is easily removed for cleaning, unlike my wife's Marlin 795 and Ruger 10/22's I have seen (you have to remove the Stock from the Barrel, to get to the Action Assembly.....).
I bought the Classic Model, that has the 2nd Longer Barrel for Target/Competition Shooting, which either has an 18" or 20" Barrel. It's still in the case in the attic. As a Shooter, the 522 is very accurate and smooth. I shoot .22LR Win 555 Walley World Ammo through it, and it has NEVER Failed To Fire..... Knock-On-Wood!
Mine came with 1 25-Round Smoke See-Through Mag, which I left in the Case with the other Barrel. Instead, I bought some 25-Round Black Dog Mags in Solid Black, from 44MAG.COM. They work great, and cycle as they should, with no hang-ups at all.
The only NEGATIVE I have to say about the 522, is that it does NOT come with any Sights at all. No Iron Sights, No Red Dot..... Nothing! It is, however, Rail-Ready for a Scope or Red Dot Scope. If you choose to buy the Factory Sig Sight Set, it'll cost you $80. You could mount an Aftermarket Rear Sight on the Rail, however, you'd have to buy the Front Sight from Sig, in order to fit the Front Groove made specifically for their Sight.
522 Sight Set
I mounted a Vortex StrikeFire Green/Red Dot on mine, and it's a perfect Scope for that platform. Here's a pic of mine:
Since this pic was taken, I have added the Sig 522 Optional Rails:
Handguard Rail Kit, Swiss Style Forend
and I added a Magpul AFG to the Lower Rail. Works perfectly for my needs!
The Stock does collapse, and it folds as well, if you need it a bit more compact for Camping, etc.
Overall, I'd give the 522 a 9.9 Rating, missing the 10, due to the absence of Sights on a $500 Rifle.
Best of Luck!