I don't have a really "stable" sponsor...up and down all the time. But, then again..it's hard to tell, since I don't send lots of traffic to any sponsor. I have the most steady ratios with SunnyDollars. Has been at around 1:350 uniques for a few months now. The $1 trials sell pretty much ok for me.
http://www.shizzn.com/x/sunny.gif