Armed with little more than the iPod and tunes downsized into the meekest of digital audio files, Apple overthrew the music distribution industry. Next, it became the world's primary online video-store outpost. Now, somewhat shakily, it's moving into sales and rentals of high-definition movies.

Apple has been renting HD movies for more than a year to owners of Apple TV, a network device. But only recently has it been selling HD downloads to computer users.

So I tried it out. I waited in line, electronically, for "Quantum of Solace," then waited (and waited) for the latest Bond installment to land (via broadband) in my MacBook. It took about 90 minutes and consumed close to 5 gigabytes on my hard drive.

The hallmarks of iTunes' music success, economy of time and space, were gone already. Compare that to cable providers, with about 43 million households already using digital set-top boxes, which can supply HD on demand without either a user-provided computer or Internet connection.

The HD downloads, at $20 (or $5 for rentals), are priced somewhere between a DVD and a hi-def Blu-ray disc. Most people probably haven't connected a computer to an HDTV. It's a bit more complicated than the familiar DVD player.

Was it worth it? Considering the time, money, effort and picture quality, no. Even at the bigger file sizes, iTunes HD still isn't quite Blu-ray quality.

No one doubts that on-demand, digital distribution is the future. The question is where it will come from: cable, satellite, Internet or your phone company? Or will it be: Wherever you want to get it?

Here's the difference. People don't care if the music they download from iTunes isn't a perfect match for a CD because it doesn't matter on an iPod. When those same people download video to watch on an HDTV, though, they'll value HD quality as much as convenience.