Not only are these an excellent bang-for-buck proposition, but they would have been a great buy at even twice the price I got on Amazon.  I bought these to replace a pair of lost Oakley Flak Jackets.  I just couldn't bring myself to spend so much for sunglasses again, so I figured I would compromise between cost/quality.  For me though, the only compromise with the Slips ended up being price--I enjoy them every bit as much as I did my Oakleys, and even more so in some ways.

My primary use for these is running.  I am an evening runner, and the fototec color shifting lenses are great for when the sun starts setting--but they get dark enough that even mid-day sun is no problem.  Fit wise, for my head the Slips fit better than the Oakleys--the Flak Jackets were just a tiny bit too snug on my face, where as the Slips are not, and the lens coverage is better.  I find build quality to be on par as well--neither these nor the Flaks have the sturdiest frames in the world, but the flexibility and light weight of both is welcome on the road.  Subjectively, the Slips feel lighter to me than the Flaks, and I frequently forget I am wearing them at all.

I would not hesitate to recommend these to anyone looking for a high quality pair of sports sunglasses that doesn't want to pay $100 or more.  Fit wise, I'd say consider these for medium to large faces.  They may be a bit too big on tiny/small faces.