Your new HD quality master is best projected via the DVI or VGA output of a laptop. Unless you have a blu-ray and HD projector set-up, you will end up having to downscale your video to standard DVD quality when you use the projector's SD inputs such as via RCA, S-Video or SD Component. That said, shooting in HD will result in better color and dynamic range and less aliasing even when down-converted to DVD.
Canon's 5D, 7D, and 550D, video quality notwithstanding, have certain drawbacks when it comes to heavy professional use. The overheating and power cut-off is a major bugbear you will have to contend with. Unless you alternate between two bodies, there's no way to shoot continuously for more than 30 minutes. There is also no swivel LCD and no autofocus.
Panasonic's Lumix GH-1 and upcoming G2 on the other hand has none of these issues. The autofocus micro 4/3 lens you buy for these cameras will be 100% compatible with the first micro4/3 sensor video camera AG-AF100 coming out end of this year. With G2, you also get intelligent track-focusing in video mode. Imagine a focus-puller built into your camera! There are also a host of touchscreen focusing capabilities. Another plus side to GH1 and G2 is their ability to record 5 minute HD motion jpeg clips as 720p quicktime. For FCP users, that means real-time editing without transcoding.
