Wagner Power Roller Max 990
Wagner invented the power paint roller, so you'd expect them to rank high in anyone's list. They've come a long way since their first units, which I can clearly remember seeing (and being skeptical about) in the store, back when I was a professional painter.
This unit comes with a variable speed pump, allowing the user to set the paint flow to match their painting speed. It also has an 18-inch extension handle, which is real nice to have. I really like using an extension handle with rollers, because it gives better control, better reach, and lowers operator fatigue. Since this is an internal feed unit, the cores of the roller covers are perforated. The kit comes complete with both 3/8-inch and 3/4-inch nap rollers.
Wagner has developed a reversible feature on the pump, along with a quick clean connector for faster cleanups. Since cleaning one of these units is the worst part of using them, that's a nice option to have.