My first MBP (core duo) had one when I first opened it and turned it on; Plus it was a matte screen in a glossy box; not a good combo. So back it went, and next week the C2Ds were released.
My current MBP has never had a kernel panic (bought Dec '06) and my Mac Pro hasn't either (March '07). I don't think they're very common, at least how I'm using my Macs.