My favorite film is VI - I find it to be far superior to II, which, while very good, is basically just a revenge story. Not very Trek-esque, as it were.

The Motion Picture would have been much, much better if they had worked to add some substance to the TV-pilot script instead of just adding very very long stretches of nothing happening. I like the concepts, but the execution was sub-par.

I haven't seen III, IV, or V in years, and I find it interesting you bring this up since for the past several weeks I've been slowly HandBrake-ing the entire Original Series to my hard drive from my library, and I just popped in Star Trek V to copy that when I saw this thread. If only that bastard who's had most of Season 3 out when it was due last week would return it ...

At any rate, I now have III, IV and V, and I'm probably going to have a nice marathon of those three in the near future. I'll let you know what I think of them after I've watched them again.