We have a Gamo break barrel .177 at work for use in the SAP (squirrel abatement program) and I have been less than impressed with it. The accuracy is not really there and it won't drop a squirrel. I have yet to stop a squirrel cold with it, even though I have confirmed hits. Joe hasn't either. I very rarely find blood, so I'm fairly certain there is no exit wound even though we have been using the pointy high penetration pellets.
If it's something you are going to haul around in the mountains and hunt with, get a Benjamin. Then you can shoot till your out of pellets. If your going to hang out around the house and kill stuff, maybe look into one that uses compressed air, not CO2. The Airforce condor and talon are pretty sweet rifles, but are a little spendy. Not the best quality on some of the parts, but good enough on the important stuff.
If you want the best (and I know you do) check out Daystate. Yeah, you could buy a couple AR15's for the cost of one of these, but you can't shoot the AR in your backyard.
http://www.daystateamerica.com/