The new UCI rule allowing disc-brakes will surely be a polarizing one, it was before it even came into effect. Those wanting to keep the sport pure were already screaming to keep 'technology' out in favor of traditional rides while others were cheering for discs to aid in riding/ braking performance.
From a traditionalists perspective, I see the need to keep the bikes pure and the riding in the hands of the racers. For me, one of the draws to cyclocross was & is the renaissance of cycling lives in breathes in the sport, where beautiful steel and ti bikes can be seen in droves on any given race weekend. Not too mention that some of the most re-known handmade builders flagship frames are cross steeds. The cross bike still looks much the same as it has since its inception complete with drop bars and skinny tires. Tubulars have seen a resurgence in popularity due to the sport, a market segment that was on the verge of disappearing, with the exception of road teams who could afford to service tubulars. I myself love tubulars as the evidence would point out on some of my favorite t-shirts with additional glue-graffiti on them from fixing or re-gluing my Dugasts. Discbrakes will not change any of this.
Personally I think beer-can and plastic bikes have done more damage to the sport that disc brakes will ever do. Downright ugly, cheap looking frames have amateurs clamoring to throw money out the window merely so that they can mimic top pros with their light-weight disposable bikes. I would rather be on a sweet steel crosser with discs that will last me a lifetime of mud-loving fun than the latest carbon bike out of China with its integrated headset, bb & seatpost. It is not carbon bikes that have done this, there are some actually stunning handmade carbon cross bikes out there, it is the paper companies and their business practices. Besides, I love my EDGE carbon wheels and other trick carbon parts on my trusty SSX.
What the lifting of the ban for cross bikes does do is open the door for both bike and component manufactures to produce disc brake compatible frames, forks and parts. While there was a small selection before, we will now see the options filling out with both mechanical and hydraulic versions in all price and performance segments. The one issue I see though is unlike its fat tire cousin mountainbiking, crossers use largely STI dedicated shifters and levers, which means more than likely this will leave most disc brake manufactures on the outside like Formula, Magura, Hayes and so on. Their will be a Shimano or Sram only systems available unless the brake guys figure some things out. Having ridden the Avid mechanical discs on a crosser, I am excited at what lies ahead. I am sure Avid will have a bitchin new mechanical black-ops/ Ultimate disc brake caliper, and you can bet your bottom dollar Tim Johnson and Co. will be on them at a cross race near you later this season.
Funny thing about the new UCI rules are that at the same time disc brakes are allowed, they also bring down the allowable tire width from 35 to 33c, which plays even more in favor of the disc brake rule. Take away handling performance from the tires by reducing the contact patch and volume, disc brakes compensate for this loss with added stopping power making handling somewhat easier.
Ultimately the disc brake rule is good for the sport on many levels. It opens the door for much better braking with little weight penalty, and when viewed with the tire regulations keeps cross, cross. It will breed a whole new segment of bikes that are actually ideal for a large portion of the cycling population out there, while pushing component manufactures to produce real road/ cross compatible disc brake options.
To keep cyclocross pure, it is up to the promoters and course designers from either making grass crits or too technical courses where mtbs/ suspension come into questions. Courses should be an excellent balance of speed, riding skills and obstacles that tip their hat to a cyclocross bicycle. It will be interesting to see how the companies answer the call to the new regulations, and I myself am looking forward to see what will be on display from some of the finest handbuilt bikes next spring in Austin.