I noticed at a cross race this weekend, that Van Dessel is now making cross frames with a tapered head tube. Looks like a 1 1/8" bearing on the top and a 1 1/2" bearing on the bottom, as is becoming popular in pro level road race bikes and suspension forks. Although it may stiffen the front end of the bike and result in more precise steering, the improvement has to be negligible given the amount of lateral flex that results when 700c road wheels are ridden hard off road. Still, I haven't ridden one, so I can't say, but I'd like to know more. The Van Dessel fork must then be proprietary, because to my knowledge, no one else is doing this with their cross frames.
Photo stolen from http://www.vandesselsports.com/