I'm thinking of getting one for my HDTV, but I'm confused. What does it actually do when you play a dvd? If the dvd is widescreen will it just resize the actual picture part to fit the screen, keeping the ratio but getting rid of the bars and giving a higher resolution? Or is it someting else?

Doesn't get rid of the bars, those are because of aspect ratio differences. Does increase the resolution from dvd resolution up to 720p, 1080i, or 1080p, depending on the dvd player.

It does upsample DVD (480i) to 720p, 1080i or 1080p, but the upsampled material will never look as good as a real HD source.

I would say it gets you about half way between 480i and 1080i in terms of image resolution, which isn't bad really.

...the upsampled material will never look as good as a real HD source.

I don't know about that -- a friend of mine showed me the difference between a quality line doubler and true HD, and unless it was Late Night with Jay Leno or the sports desk on ESPN, I could not tell the difference. Films, CGI animation, TV shows like CSI, ER, etc. were indistinguishable.

I don't know about that -- a friend of mine showed me the difference between a quality line doubler and true HD, and unless it was Late Night with Jay Leno or the sports desk on ESPN, I could not tell the difference. Films, CGI animation, TV shows like CSI, ER, etc. were indistinguishable.

Move a foot or two further back from the HDTV and the Leno/sports desk difference you saw almost certainly becomes indistinguishable as well.

Doesn't get rid of the bars, those are because of aspect ratio differences. Does increase the resolution from dvd resolution up to 720p, 1080i, or 1080p, depending on the dvd player.

I still don't get it... what I mean is does the image take up any more space on the screen? Or is it just more detailed?

More detailed (if your display allows it).