Last season, Martin shot 44.1% from the field and 37.0% on free throws while averaging 4.3 rpg or 6.9 rebounds per 36 minutes. I'm just not convinced he is worth signing.
This is the key with Martin. If he was the Kenyon Martin of 10 years ago, you sign him without a second thought and deal with anything that may arise. However, he just isn't an impact player anymore. He may not be as good as the guys you already have, and could then just be an extra headache with no real advantage.
It would be different if the C's really were desperate for help, but they really aren't. They need to continue improving with their team defense and rebounding, but there aren't many guys on the street who are going to come in and make a big difference with that right now...any more than the improvement of guys becoming more comfortable in the system will.
Yes, the C's may need to get an upgrade in the frontcourt if they want to really have a good shot at a championship, but that is not Kenyon Martin (nor is it Chris Andersen, or anyone else currently out there).