Midnight T,
I breed Labs. Pretty much goes without saying that I love the breed and most of the individuals in it.
That being said, be aware there's been a lot of indiscriminate breeding going on. This can result in a dog that is totally "non-typical" with respect to "standard" breed characteristics. IE, while generally the Lab population is considered a gentle, loving breed, you can get a mean one.
Find out why the dog is in the shelter. If put there by previous owners, call them up and ask them WHY he's in there. Sometimes its as simple as they were moving and couldn't find him a home. Other times it can be because he bit the crap out of their kids or something.
Try to find out whatever you can first. Second, tell the Shelter you'll take him and love him on a two week trial. Then be realistic in the two weeks. If he has faults admit it and decide if you can still live with that fault 3 years from now.
Good luck to you. Rescue him if you can. A good Lab is a marvelous friend and companion.