Hi Deb,
I know it is expensive being listed, but from my own experience our sites have been crawled by all of the major search engines much deeper since getting listed in Yahoo.
We went from 500kb per day to 28mb every other day. Our
PR went straight to 4 within 3 weeks of being live, maybe a coincedence of the update schedule but all our sites as a rule have become more popular.
It is also a good tax right off as well!