For those of you who keep kosher and have been replacing the butter with margarine, from now on use Earth Balance.
I use it and don't keep kosher, that's how good it is.
If you care it is also good for vegans and halal. The real issue though is taste, consistency, texture and health.
I use it as a replacement for butter in almost all my recipes nowadays, and kashrut is not an issue for me.
Here is there website: Check them out. http://www.earthbalancenatural.com/