"dkeller, this is true but the black bars on a 16:9 display will be much smaller than on a 4:3 display. I agree with PJ, it's a matter of preference."
Sure - but he did state that he "didn't want to see black bars on movies", which is unavoidable, although they can be minimized. Personally, I can't see why anyone would want a high-end 4:3 projection tv, principally because there isn't much of a price premium on WS HD RPTVs, and beam spot size (among other things) are optimized for the aspect ratio of the screen. Moreover, most 4:3 sources are relatively low-rez compared to 16:9 and 2.35:1, so you would naturally want a smaller display for 4:3 and a larger display for 16:9.
That is, if you primarily watch movies and HDTV. IF you're a sports addict, it makes a lot of sense to buy a 4:3 HD RPTV. With direct-views, however, it's a different story. THe price premium for a 16:9 tube is very large, so economics may out-weigh picture quality considerations.
Regarding bandwidth on progressive DVD players: While it is true that a 480p signal has a higher bandwidth than 480i signals, remember that the 480p signal is generated on the player (all current prog. DVD players start with an interlaced signal). So while it's true that your tv set will see a higher-bandwidth signal, you really can't generate more information than what's on the disc. The principal reason for a progressive player is bettering the line doubler in your tv and avoiding a D/A conversion before the line doubler (the scaling from 480i to 480p inside the player occurs in the digital domain).