If any of you live near a really high end AV store, go check out a terranex scaler. We ran laserdisc through a terranex and the results are absolutely mindblowing.
Also, if you have a fixed panel display, (like plasma, LCD, projectors and so on) having an image scaled professionally to a 1:1 pixel match for your display looks much much much better than the job the crummy internal scaler in your fixed pixel display does.
If you took the time to do it offline with the latest technology and then play *that* rsult back - you wet your pants.
Now the argument goes that you can't get back information that isn't there in the first place, but sometimes you can.
If you have a sine wave that has been samples at a low bitrate, you get a blocky representation of a sine wave. If it was audio, it won't sound like the original.
If you take that blocky sinewave, and convert it to splines projected through it, and sample that at a really high bitrate you will end up with a smooth exact match for the original sine wave and it will sound just like the original.
With video it is a lot harder, but some new algorithms presented at Siggraph last year do an absolutely amazing job, and if you have a HD device, a pro scaled image definately looks a LOT better than feeding it 480i or 480P from your DVD player (unless you own a terranex)