I joined it around May and had no results for a while until end of June. Now in July, I have 3 links sold by text link ads.
The bigger your website is and the more it's visited, the bigger your chances of getting good results are, pretty much like trying to sell text advertisement on your website. So far, I guess like 1 additionnal advertiser per month (It's been 2 months so far).
I was very tempted too at one time especially when they were giving out a $100 off for a purchase of $120. But the links were not suitable for my sites and therefore, I have not done so. I feel that text link ads is good because they are up to date with their payment via paypal.
Yeah text link ads are cool, I my site with them and they pay good $$$ for putting other peoples ads on your site. Your site needs to be PR4 or better to benefit though. As far as buying I have never done that but there are stacks of sites to choose from. My site have over 6K of pages with link ads in the footer on every page, so when they come to me they are getting a good deal anyway.