Tom, I'm familiar with Team Unlimited here in Hawaii and have seen the Xterra market take off from a few mainland races to the global presence in about 3 years. On Oahu there are only a couple of off-road tri's but they are very popular and fill to capacity. Most of the serious Hawaii triathletes I know seem to really like the off-road races (although guys tend to get into them more than the gals). For myself, I love off-road triathlons -- the mountain biking is challenging, requires balance, technique, guts, much more bike knowledge, etc -- and you are really fried (whole body) by the time you crawl off the saddle and start the run. A great way to recover from the mind-numbing long training rides for an ultra-tri. And the atmosphere at the Xterra races seems to be a bit less competitive with a sense of "us" against the "elements" -- the lava rock on Haleakala on Maui doesn't care if you're a pro or AGer...