Then again, how good does a Blu-Ray disc look when being played on a non-HD TV?
If you don't have an HD-TV, then it doesn't matter. DVDs are made for SDTV: 720x480 resolution. If you have letterbox movies, then they're really swished. If you're okay with that... I mean, even VGA is 800 pixels across... that means SDTV is less than VGA quality. You may as well watch the DVD on your computer and it's a better quality than your non-HD TV.
You will need at least a 720p resolution HDTV to enjoy Blu-Ray. But if you really want the full impact of HD quality, your TV should support at least 1080i. That's about 2.5 times more than SDTV and that's why it's so much sharper.
If you have an HDTV and still playing DVDs, then you're cheating yourself and the TV. Playing a 720x480 video on a 1920x1080 screen is like riding a bicycle on the autobahn.
Also, Blu-Ray players plays DVDs, so you won't "have to" replace your DVD collections. Many players also upconvert the image to HD quality (not true HD, but resampled) so your old DVDs will look sharper. Also, DVD is MPEG2 compression, so you will notice pixelations (especially during action scenes) and other compression artifacts.
Not all Blu-Rays are created equal. I watched the Blu-Ray version of Dracula and it was not very good, because it's not digitally remastered for HD. In fact, it looks worse on the HDTV because the film grains are amplified. But when I watched something that is "reference material" like Peter Jackson's King Kong or Disney's Sleeping Beauty or WALL-E, the quality is incredible. You can absolutely see the difference between HD and DVD.
It took more than five years for DVDs to catch on and now people talk about DVDs as if they've been watching them forever. I still remember the snarls and disdain I heard when DVD players and movies first came out, especially from those Laser Disc aficionados. Now they're all clamoring for HD.
