Until now, HD video-sharing sites have been few and far between, and none have used the universally accepted Flash (the same format YouTube employs for its standard-def clips).
Since high-def video tends to choke bandwidth, you'll need at least a 1.6Mbps broadband connection to appreciate it – otherwise DailyMotion will scale it down to an appropriate res.
You'll also need hardware that's built to cope with HD video, though a hefty single-core PC or any dual-core machine should handle it admirably.
We had a go today and found a smattering of clips already up. Stay tuned for more though, because hi-def National Lampoon sketches and clips are promised.