Sure would! As long as the price is comprable to Netflix as an example I would but an

TV in a heart beat! Been patiently awaiting this!
2 or 3 people have mentioned Netflix ...
I have to agree that this sounds GREAT. It would probably make me buy an

TV as well as go out and get an iPhone (as was discussed in another thread, I just chose a Nokia N800 over an iPod Touch, but am still open to an iPhone).
And, a few months ago when there were discussions about "subscription model for iTunes", the thing I, and a couple others, kept bringing up is: I don't tend to buy movies, I tend to rent them. Sounds like someone at Apple was paying attention. But the added wrinkle is: I don't rent them per-movie. I rent them by subscription, via Netflix.
And that's what this is going to require for me to buy in: a subscription option.
Ideally, I could have all 4 choices available:
1) Buy individual music (songs/albums)
2) Buy individual videos (movies, TV)
3) Subscription of some form for music
4) Subscription of some form for videos
If the subscription model is "unlimited per month" (as netflix is in theory, but not exactly in practice*) then that'd be good. In fact, that'd be best.
(* netflix will throttle your exchange rate to be slower if you're turning around movies too quickly, so you might get 2 day turn around if you're only doing it once a month, but if you do it every 2 days, you can expect to start seeing 3 or 4 day turn around after a while ... at least, they used to ... there might have been a lawsuit about it, and I don't remember the outcome of that)
If it's "X movies per month", then I'd almost prefer it to be "X movies per payment" ... so if I get 5 movies per month, and I rent all 5 in the first week of October, I can either wait until November for 5 more, or I can pay again and get 5 more movies during October. Further, if I'm going to be in Timbuktu for a month, I can not pay for that month since I probably wont use my 5 movies.
But, as I said, unlimited per month would be best.
I'd probably not only ditch Netflix at that point, I'd ditch HBO, Showtime, and a few other things. I might keep enough DirecTV/Cable to catch the Discover/Science/History/Learning channel stuff that doesn't seem to be on the iTunes store ... but that might be about the extent of it.