I acquired one of these keyboards last month. Prior to it, I had been using a CM Storm Quickfire with Cherry MX Brown switches that I thought were really great. The HHKB blows it out of the water -- the switches are very silent, give great feedback, and the typing experience is second to none. The biggest downside in my opinion is the lack of possibility in trying one of these out before you buy -- I've heard Topre switches are hit or miss for a lot of people. It certainly takes some getting used to, and it slowly grew on me over the course of a month.
Product Kitty