Personally, I think Apple should buy TiVO. Either that, or launch a similar product, which sits in your living room and networks with your Mac either via Airport Extreme or wired Ethernet. Then, you could browse the Quicktime store, download any movies you want and watch them in your living room or on your computer. I think they should be in MPEG-4 with 5.1 AAC (Pixlet was never meant for this purpose). The nice thing about MPEG-4 is that when people's connections improve, the quality can be scaled up.
Also, this set-top-box could record TV programs directly to your Mac's hard drive in MPEG-4, and maybe even have a superdrive in it for DVD recording (it would then record in MPEG-2, obviously).
I don't think it should be able to burn the downloaded movies, though, as this would a) piss off the movie companies, and b) result in bad quality due to the MPEG-4 to MPEG-2 conversion (lossy-to-lossy).
You could even use it to browse the store in your living room with your remote control! How cool is that? The quality would be good, too. MPEG-4 can be as good as, or even better than DVD-quality. Of course, it would need to be encoded from the original uncompressed version, not from a DVD.
Despite all this, I don't think Apple are ready for this just yet. They need to wait for people to get faster connections, or more specifically, for more people to get the fast connections that some already have.
As much as I hate it, I think DRM will probably be essential for this movie store. There's NO WAY the movie companies will sign otherwise. It will probably be heavier DRM than in iTunes, too. I reckon we'll be lucky to get one burn of the movie. And it won't convert to DVD, either, as this would sacrifice quality. Instead, they'll just let us burn a DVD with the original MPEG-4 on it (if they let us burn at all). But then, if they release a set-top-box (which I know is far-fetched, it's just an idea), we won't need DVDs. Especially if they make it cheap.
Of course, there would be other boons to releasing such a box. Not only could it play your movies on your TV, it could be used to play your MP3s and AACs in your living room, through your stereo or TV, maybe even displaying an iTunes visual on your TV. They could easily make a version of iTunes that is navigable via a remote control. With the superdrive, you could also burn CDs in the living room, and rip them, and have them ready in your iTunes library on your mac. That's the beauty of a networked solution over a stand-alone product that just records to a built-in HD. It could probably do the same with your iPhoto library; displaying slide shows with music and fading effects, ripping Photo CDs, burning Photo CDs and DVDs etc. And, of course, it could do all the stuff that a normal TiVO can, like pausing live TV, rewinding etc. The possibilities are mind-boggling.
Of course, there's no evidence to date that I know of that Apple might be pursuing something like this, I just think it would be a good idea for them.