Smeg my post disappeared and I'm getting tired. When tvs get bigger it becomes a lot more noticeable in terms of resolutions. I have a 14" laptop, can play high def stuff on it, and it looks great. I have a 26" tv that 720p stuff looks great on but beyond that size the benefits of a higher resolution become more noticeable.
Material and uses-
PS3
X-Box 360 (ish, complicated)
Blu-ray/HD DVD. One of these days they'll sort these things out and even release more material and people will buy them.
Use you tv as a monitor sometimes, 1920x1080 mmmmmm!
Digital tv will have high def channels beyond sky(initially 720p but 1080i oneday maybe and beyond?). Freeview will have 3-5 channels when a plan to kick other channels off a multiplex kicks in. Freesat will probably have 5 terestrial HD channels. These will be free and available to a very high percentage of the population if they buy the equipment. Unlike sky HD which has very low figures now.
Hopefully your tv will last a good 5-6 years at least and in that timeframe some of these uses will come to fruition. These would look good on a 720p anyway but 1080p is in now. There are a lot of weird and wacky articles on 1080 but most of the subtleties are good points.