i have the same experience like garyr_h. I'm over the top in Bing from day to day, while in Google i'm loosing traffic every day. Also what caused this rise in Bing is the 1000s of changes since January, which made my website 4 times faster, i removed all duplicate content, and also removed any possible keyword stuffing/spammy content. While in April i've been punished by Google (i assume by panda). I've been highly rewarded by Bing. I have the data from pre panda for my important keywords, and results on first page are getting worse and worse(nearly all of them are spam). While before me and my other competitors(who i also think are good sites) were on first page, now all of them are new, "just made for spam" sites.