After having read this thread, I bought some fermcap. I've used it in the brew kettle for my last 3 batches and can say without any hesitation that I just can't stand the fact that I had never heard of this stuff before this thread.
I brew on the stove top in 8 gallon brew kettles, so for 10 years I've been dealing with the threat of boil-over. With fermcap I don't have to worry about boil over any longer.
Long live fermcap... I'll never brew without it again.