Guys, if the glass is slow to move chances are the rollers are flat on one side and so now they have to slide back and forth with the window moves up or down. The tracks they ride in can and will get wet when it rains due to water running down the glass and past the weather stripping. The tracks will hold water due to the shape and eventually get rusty. As they get rusty they are no longer nice and flat/smooth for the rollers to move over. The rollers snag on the rust and stop spinning, but the force of the motor or manual crank overcome the resistance and begin the process of grinding them flat on the bottom side. Pretty soon the nylon roller wears down to the rivit and you have metal on metal contact, plus the arm that the roller is rivited too is not centered in the track anymore. Between the mis-alingment of the arm to the track and the flat rollers sliding on a rusty track they eventually "freeze up" or stick.
Like I said before in an earlier post, when the regulator sticks due to the rollers, the power motor can overheat, strip the gears or break the cable (manual windows usually break the crank arm). Lubed up with new rollers and clean tracks I can turn the manual crank on mine with one finger. It don't take much to pull the panel off the tailgate to at least look at the condition of the rollers and tracks. It didn't take that long for me to drill off the old rivits and install the new ones with the regulator removed.
. goin up is a different story some times it will and sometimes it wont. the regulator cable keeps gettin pulled out 
oh well i dont use it that much anyway.
