I don't think Hokey Smoke or Todd Christopher read the link in Hokey's reply. If they read the whole thing they would realize that there is a difference between "Video" mode & "film" mode deinterlacing. read all the documentation in Hokey's & Jim209's links for the details. Most TVs only do video mode deinterlacing, which only creates a close approximation of original frame structure. This is what Savageone79 was referring to, but what he is unaware of is that most DVDs are from film source & are encoded with the full frame structure available to a progressive DVD player. Almost all Progressive DVD players (except the Pioneer 434) do film mode deinterlacing which is far better because it can create, from film originated material, original complete frames.
The actual movie part of most DVDs have very good flags & rarely cause a progressive DVD player to drop from "Film" mode to "Video Mode". If you would have read HometheaterHiFi's whole article you would know these things.
Please don't give advice if you don't have a thorough understanding of the topic, if it's technical, provide a link & let the respondent make up there own mind.(Like Jim209 did)
With the prices of Progressive players getting very reasonable(I just bought a JVC that had a MSRP of $899 six months ago for $280 last week) I'd definitely get a progressive player!
Also one of the biggest advantages that no one has mentioned yet, is that many TVs will only do anamorphic compression on a progressive source, so you will lose 30% of your vertical resolution on Widescreen material if you have a 4:3 HDTV set and don't use the component digital inputs, which require a progressive source. If you have a widescreen set, this doesn't matter.
Hope this helps,
Mike G