The issue of using "HIIT," or high intensity interval training, had come up in another thread as one approach to preparing for the "endurance" demands of skiing. http://www.scienceofrunning.com/2012/01/crossfit-endurance-tabata-sprints-and.html this blog is a helpful summary of some of the issues, and helps explain why for skiing, racers for one example don't generally use HIIT protocols for building their endurance base. (A portion of their overall workout plan may use HIIT intervals, but this is very different from relying on HIIT training as a primary means of building "eundrance.") I note that the blog reads as anti-Crossfit, but some of the comment section do correctly note that there are isolated CrossFit boxes that might not follow Crossfit as far as training endurance. To me, the real issue is whether people are grounding what they do empirically -- e.g., the commenter in response to that blog who boasts about his 18 minute 5k doesn't seem to realize that an 18 minute 5k isn't even a normal high-school varsity time, much less an impressive time, so doesn't really have perspective on what works best from a conditioning perspective.
For skiing, this all translates to meaning that the pyramid of time spent training at different intensity levels for developing "aerobic" conditioning for ski racers applies equally to recreational skiers who want to get slope-shape (though, time restraints might support a bit steeper pyramid). As Warrner Nickerson mentioned in the recent skiracing mag, "Let's hope you put some work into strengthening your quads and hammies, and increasing your aerobic threshold, too."