I have two metronomes that I've hardly used because, like most guitarists, I assumed that my internal beat clock was good enough. I'm discovering that's not so. I've observed that I have this tendency to speed-up my tempo as I'm playing Music For Dreaming.
I tweeted my problem and Joe Lewis (aka @sanbeiji) wrote-up a blog post for me on how to use the metronome properly. I'll try to put his recommendations to use.
Christine Dunaway (aka @fddlgrl), who teaches violin, also clarified that I should be technically comfortable with the piece (or whichever segment I'm practicing) before using the metronome.
As luck would have it, an old topic was resurrected on delcamp.net which linked to a website on Metronome Techniques. Synchronicity?