I had been happy with a Boar's hair brush, but I came across a deal on eBay. It was a "The Art Of Shaving" pure badger brush, which retails for $55 on their website, new for $30 with shipping. The difference is night and day. I don't know why the type of hair makes this much of a difference, but the lather was 3 times as thick, felt better on the face, and the brush actually smells a lot nicer.

I know I am the millionth person making this realization, but I needed to add my 2¢.