I bought these boots in preparation for a January weekend of steelhead fishing, wherein we'd sit in a metal drift boat for eight hours at a stretch in temperatures around 30 degrees.  Since these boots were rated for really, really cold weather (I believe somewhere around minus 25 degrees), I was hopeful they'd keep me warm and comfortable despite not generating any body heat of my own to help them out.  Suffice it to say, they didn't quite do the trick--hence the four star rating instead of five.  While I didn't suffer too terribly bad (no frostbite or painful rewarming), my feet were definitely chilly after several hours, even with huge wool socks added to the mix for good measure.  (I bought a half size larger than I normally wear so I'd have plenty of room for the giant woolies.)

On the up side, they seem well made and should last at least ten or fifteen years.  Yes, they are heavy and bulky, but in my opinion that's a small price to pay for relatively warm toes.

As another reviewer said, if you're looking for boots to stylishly run to the supermarket in, these aren't it.  But if you need something durable, functional, and relatively warm, you might give them a try.