Use a Blu-ray with one of the newer 1080p sets and the difference is HUGE.
It is a huge difference, but it's also not a fair comparison to make. Unless you have a decent up-converter / single adjuster - a standard definition DVD (or any other content) tend to look WORSE on many HD sets. (then the same content would look on a similar sized standard set)
A good example is hooking up my PS2 to my Dell LCD - games looked like trash - in spite of my LCD being 720P. Hook up a PS3 to the same LCD - and a PS1 and PS2 game looks WORSE then they would on an analogue CRT monitor or TV. (a lot worse, actually) But the second you enter the realm of 720 - it goes polar opposite and looks great. But only for content intended for 720.
I agree that HD 1080p content on an 24" LCD looks great (obviously smaller size makes image discrimination rapidly diminish over distance) But again, feed it a lower definition source - and that source is "prejudiced" against by the newer format. It's like having a nice VW thats in great condition, and then parking it in a Lamborghini dealership parking lot. Yeah, it looks like a cheap POS - but only because of outside influence.