I'm not too picky with butter, but to support local'ish farmers and good animal welfare dairy farming, I tend to pick Strauss or Organic Valley (of course Organic Valley sources differ from region to region)
Me three, where baking is concerned. For health concerns, I switched to Smart Balance for spreading. I wish it were unsalted but suspect that if it were, it would have little taste. As Frankenspreads go, it's pretty good.
Keller's all my life. However, I recently discovered Cabot's so when I see that brand I go there now (not widely available in my area). Although we get Kerrygold cheese in my area, I've never seen their butter.