I also think that HD should be central to any TV strategy the NHL puts in place. There was an article on some site (espn or si I think) along the lines of "I guess Tiger was great at the British Open, but I didn't watch since it wasn't HD". Going on about how he'll watch crap movies just because they're in HD etc. Sure, it's a case of being enamored with cool new technology, but there's an audience out there that will likely tune in just because it's in HD.
For the NHL, I think there are two factors that HD can help with. First, the higher resolution widescreen picture is just better for covering the action, and since so much in hockey happens away from the puck, it's more beneficial than in most other sports. Also, though, I think it opens up the possibility of more creative coverage 'tricks' - multiple synchronized split screen views to watch play develop from different angles (maybe best in replays). P-in-P player (or coach) isolation with enough resolution to be useful. Sidebars with running stats etc.
Of course, all the above would be even more interesting in a broadband/streaming setup with destop stats tools etc, but I don't think we're *quite* there yet in terms of bandwidth to make this a primary strategy.
Brainstorm question - What would be your reaction to the NHL developing something out of video-game technology where they distribute a hockey 'engine' (based on NHL 2005 or something) and make available via the web site a weekly package of 'highlights' which are scripted versions of the plays of the week, translated into animated video game format. The idea being that you could watch the original video highlights, then explore them 'in game' in 3-d with the ability to pause, change perspective etc. Do it with educational content/ analysis as a tool to bootstrap understanding/insight of the game. Has the cool/fun factor, and if you're not careful you just might learn something.
Of course, I'm not sure how feasible this is - are existing motion capture tools good enough to make this easy/cheap enought to be viable?