When I was between jobs and after Cobra, I also looked into dental insurance. For us with 1 kid, it was just about break even for checkups if paid out of pocket vs. with insurance. However, all it would take would be a root canal, a crown and/or a filling to put it back over the edge to being very worthwhile. But right after I started coverage, I went back to work and had to cancel it.
By the way dentist was more than willing to work with me and gave me their shelf prices for all of the common procedures. Really helped me make the decision.
Also, be aware that there are lots of "discount" plans out there that are not insurance. If you have a dentist you like, make sure before you enroll that they'll accept the discount plan or insurance and that you know what your out of pocket will be for common procedures.
Big-Papa