We moved from Yahoo to CBS and we are split about whether or not to move back to Yahoo. There are many things to like and dislike about both sites, so I'm on the fence myself. A lot of it depends on the type of league you have... keeper league: CBS. funky rules/settings: CBS. More straightforward league: Yahoo. Beyond that, it is really just personal preference. Though I do like looking at Amber Wilson every day on CBS
I have no experience with ESPN except to know that they had a LOT of problems this year that they busted tail to fix. Sometimes that can be a good thing though, as the major problems can shed a lot light on what is important.
"The government cannot give to anyone anything that it does not first take from someone else"