Joel Spolsky has an interesting article about the difficulty of identifying an exceptional programmer if they are using Java.
To quote:
The recruiters-who-use-grep, by the way, are ridiculed here, and for good reason. I have never met anyone who can do Scheme, Haskell, and C pointers who can’t pick up Java in two days, and create better Java code than people with five years of experience in Java, but try explaining that to the average HR drone.