It does. Opinions vary widely on it though. My view on it is that if you have half decent eyesight then it's obvious on 26" and above screens, whereas by the time you get to 37" it is scream in your face obvious. Other people say 32" is the minimum. On this basis that's still a yes.
The problem is the picture quality varies enormously for what reaches your set it ranges right through from pretty good such as BBC1 right through to godawful picture quality on things like news and music channels and a few middling names like ITV4 that should be a lot better than they are but sadly aren't.
Thinking of tangible examples for you, you watch some terrestrial football don't you smokin Joe? There's a gigantic difference between ITV1 (one of the weakest channels picture wise) and ITV1 HD. Formula 1 will be in HD for this year, which I reckon will be a huge improvement from the extremely irritating mushovision we had to endure with ITV and the half decent picture on BBC1. Unfortunately MOTD isn't in HD yet, but as we speak they are working hard on studios in manchester which we are promised will mean so. It should also mean (theoretically) that a lot of other BBC sport makes it into HD, although I wouldn't hold out too much on that one.
Whether it is worth buying is up to you. You'll only get BBC1 HD, BBC HD (a weird mix) and ITV1 HD. At present. That may and hopefully change in future. Unfortunately a lot of other HD versions of the sorts of channels on freeview and freesat are signed up to contracts with sky. They may appear on freesat eventually (3,4,5 years down the line). For the money, if you're going to get a HD receiver I'd get a humax and get the PVR recording facilities. It's more money, but worth it in the long run imho.
