As I mentioned before the karma scores were all reset to 0 and the weightings for the algorithm were totally changed to reflect a busy long standing forum like ours.
With that in mind I suggest you use it if you want to, and give good/bad karma points to posts you believe are valuable or viceversa.
Remember though, karma is given to posts, not to people. With this I mean that you are scoring the individual posts people make, not if you like or dislike a person opinion, posting style, etc.