I watched Appaloosa last night on Blu-Ray and it was of spectacular quality, like just about all of the Blu-Ray titles I've seen.
Every now and then you'll see one that's sub-par, but Blu-Ray compared to regular DVD is like night and day.
The PS3 is connected using HDMI. The TV is 1080p and the HD cable channels we get all look spectacular. It could also be the movie itself. I still buy Blu-Ray titles when they are ridiculously cheap so I have some others I can try. But unless every movie is spectacular, Blu-Ray is a non-starter.
I bit the bullet and bought a Blu-Ray disk player to go with my Hi-Def tv. And cannot see enough difference in picture quality between Blu-Ray DVDs and standard DVDs.
Now if you're talking sound, then yes there is a difference, but as far as picture quality, the added cost of the Blu-ray disks just isn't worth it.