Pros
I was referred to Stacksurfers by a friend when looking for a position in 2012.
They didn't have anything for me at the time. After a pretty extensive discussion with one of their Recruiters, I was told they had a clear picture of my requirements and would contact me immediately once they had a fit.
I wasn't surprised by this as I specialize in Machine Learning; Bayesian Probability Algorithms, backpropogation, etc.
True to their word they contacted me about 4 months later with a position. Minus the commute being a bit of a grind it was perfect for me in every way.
I've been happy, and incredibly busy, at my new company for over 5 months.
Cons
None that I can think of.