NTSC Video is recorded with about 60 interlaced fields each second while motion picture film is recorded at 24 full frames per second. So it makes sense that if you have a camcorder that will shoot 24 or 30 full frames every second, what you shoot will look more "filmic" (or at least less "videoey") in its motion.
To be precise, NTSC camcorders ALWAYS shoot in 60i– but are able to vary their field cadence to simulate 24 fps or 30 fps footage.
I usually shoot in 30p (or "30f" on the Canon H1 & A1). The only time I shoot in normal, 60 field interlaced mode is when we’re purposely trying to get a videoy look- to make something look "broadcasty" like a news or sporting event, soap opera or reality show.
What about 24p? I might get flak for this, but I actually prefer shooting 30 fps to 24 fps- even though 24 IS the frame rate of film, 24 gets too "stroby" or "staccato" on some camera moves, where 30 is just a bit smoother- enough to take some of the "staccato-ness" out while retaining the cool, filmlike, unvideolike motion look.