It does depend on how well off you are. Personally I feel that SKY is far too expensive as it is. I cancelled my subscription 2 years ago and have never looked back. I have saved nearly £700 which is quite a lot of money to me. I still have my dish and box, so all the important channels are still there. But I don't have all the rubbish ones. Life is far too short to spend hours watching old 1970's programs, or endless repeats of Top Gear. !
However, that is not the point of you query, and I have just been letting off steam !
I agree with ChuckFickens. On small screens the difference is neither here nor there. But if you have a huge TV, than you will see an improvement.
Also don't forget most of the proper channels, like the BBC are broadcasting in HD all the time, even if you don't subscribe to SKY HD.