To update anybody who might be interested...
... with the help of other users, I've recently devised a way of playing my iTunes HD content through a Popcorn Hour media streamer to my 42" television. It's the first time that I've been able to do any side-by-side 'Blu-ray vs. iTunes HD' testing, and thought I'd offer my opinion on the results.
In a nutshell, Blu-ray is appreciably better. The colour is more vivid, the detail is more crisp - if you're a hardcore videophile, iTunes HD isn't going to do it for you. Added to which, the audio is AC3 - on a Blu-ray disc, you can expect all sorts of glamorous HD audio formats that iTunes HD is never going to give you.
However, iTunes HD offers me certain benefits that make it, I think, my new format-of-choice moving forward. Among them:
1). iTunes HD files look better than DVD rips, and sound as good (DTS tracks excepted...). They also tend to be slightly smaller.
My DVD collection comprises almost 800 movies and God-only-knows how much TV. Some of these discs are more than 15 years old, and starting to degrade. Much as I would like to replace everything that I have with Blu-ray discs, a). that would cost me many thousands of pounds, in both Blu-rays and additional hard drives to rip them to, and b). I don't have the tens-of-thousands of man-hours required to rip, de-branch, remux, back-up and catalogue 1,000-plus Blu-ray discs. When I was a university student I would spend whole days doing this, but now, it's not even a question.
2). Now that I can move the files between devices, iTunes HD is essentially a universal video format - I can sync them to my iPad or my MBP when I'm on the move, watch them downstairs on my PCH when me and the girlfriend are having a 'movie night', or if I'm in my office procrastinating on my new iMac (which I'm going to buy soon...!) then I can have a movie running in a window on my desktop. This is priceless.
3). As I've said before, you can't beat the convenience of first spotting a movie on the iTunes Store and having it in your possession in under 10 minutes. Sure, you might be able to get the Blu-ray shipped next-day through Amazon Prime, but the immediacy of iTunes is great for someone like me.
So, then - for someone with my needs - in conclusion:
Blu-ray = excellent quality, poor convenience
iTunes HD = good quality, excellent convenience
Only you can know which is more important to you. Personally, now that DRM is no longer blighting the issue, it's a no-brainer for me.