I've got one, used mainly for polishing and refining, as I use rotary's for compound.
Really nice piece of kit, I use the 3 inch spot pads if i'm concentrating on individual panels or the standard 7 inch for general polishing and waxing the whole car.
As with everything, it depends what you want to use it for but it's a good all round tool, you can use compound with it too, obviously with the right pads. I'd recommend 3 inch spot pads in soft, medium, and dense, and, (if you need to) another larger dense pad for compound.