I never left Google. I just put one site on Yahoo to test. It didn't take long to see what the issues were.
It's all about the bottom line. AdSense is better for me, but for you maybe not. I don't care about $$ per click. I care about what my monthly payments are. I'd rather have 50,000 @ 18 cents per click on average than 5,000 clicks @ $1 per click on average.
till now tested only google... and have bad experience and now google is not approving me again for a different site... not tried yahoo but trying bidvertiser... they dont have huge advertisers but paying honestly... not like google