Indeed, thank goodness Kasdan is there. I'll try and stay optimistic.
Star Trek: The Motion Picture is just not a good film. It had a troubled production history, among other things the script was a re-write of a planned pilot for another Trek series, and suffered from constant tinkering from many different people even during shooting.
To be frank, even as a hardcore trekkie I find it boring, the pace is glacially slow and it has the worst possible influences from it's time (think '2001: A Space Odyssey' style of very long shots of spacecraft slowly moving). It hasn't aged well at all, I would avoid it unless you've seen all other trek movies (although there are some other stinkers out there, e.g. Star Trek: Nemesis is rubbish), it's only worth watching if you're dead set on absorbing all Star Trek, it would be better to watch some TNG, Voyager or DS9.