As a tool, depending on how it's implemented, it is fine to have. The problem comes with the way people deal with the information this tool provides.

If there is a gear check for high-end content, fine, but I want people to understand that to get good gear, at some point you have to run with not-so-good gear until you are able to win a few times. By shutting out all people without "X" gear score, your beginning to limit the number of people who have access to obtain said gear that you want them to have. However, since this is happening right now without a visible score, I don't see this concept changing any time soon.

That said, I'm really curious to see how a gear score would be calculated. I have a pair of nicely melded Felt Trousers with STR and VIT that I use for my WAR and for my MNK. The pants are better for WAR because of the VIT, but they're still useful for MNK. (and before you say "Felt? why not DL? n00b!", this is just an example) Will the pants have the same score regardless of job, or will it be variable?

Once we have a better understanding of the calculation method, then we can start determining if this will be a useful tool or not.