What I've found is that Dave seems to use the Neck PU in the beginning of solos, but as a solo peaks in energy, he sometimes switches to the bridge pu in order to totally take it to the next level.
I recommend the David Gilmour Live in Concert on DVD, its worth the $20 bucks i paid for it. I'd pay $30 for it, if that was the price. It showcases acoustic rhythm guitar playing, accompanied by the every once in a while Dave putting the electric guitar on and ripping solos. It works beatifully.
The style of music Gilmour plays seems to put me in this 'trip', if you know what i mean. It's that mellow, check him out!