I used a paintmate plus (about $25 at home depot) on a project today and I LOVED IT. The room had really high ceilings and I could just reach the top of the wall when the paint chamber was full.
Awesome concept- I flew through the job - no mess, no drips, takes about 4-4 loads from a gallon of paint (not many at all in my opinion. Has to be better than dragging a hose around with a power roller and a lot less $$.
I was sceptical, but I'll never paint without it after one try.