I have a 3 pickup LP Custom BB. At first, I though the way most people do....that the middle pickup will be in the way, or useless.
NO WAY! I really like the middle pickup feature. Even when it's lowered a bit, it still picks up the sound just fine.
On these guitars, the 3 way toggle is
Treb = Bridge pup only
Mid = Bridge and middle in parallel (like a sweeter version of a normal Paul's middle) Great for clean playing on a Paul!
Rhythm = the neck pickup only.
On mine, I have Gold covered Custom 5 bridge/59N/59N.
SMOKIN combination!