I feel like an idiot. I do quite a bit of searching around on the internet and yet somehow I didn't check the manufacturer's website. Go figure. The mechanical advantage gear ratio is 5.4:1 according to their website located below. It claims the maximum rated capacity is about 1,500 lbs. If my math is right you need more than 250 lbs of turning force to raise a 1,500 lb branch. I don't see myself doing that anytime soon. That compares to the GRCS which would require either 34 lbs of force or 68 lbs of force depending on which gear ratio you went with. Of course it would take 4 or 8 times as many revolutions so I guess it's a trade off. You can attach a heavy duty electric drill to speed things up and to take some of the work out of it which is nice. I wish the RCW 3001 could do that.
http://www.steinworldwide.com/proddetail.php?prod=SS-RCWINCH
Nick, just a suggestion but putting that gear ratio in the product description on Tree Stuff could be useful for people comparing the RCW 3001 to the GRCS.
EDIT: I would like to note that I realize if I was working with a 1,500 lb limb that I wouldn't be lifting the entire 1,500 lbs(at least initially) since it would be hinged at the base of the limb and the force tension would probably be coming at an angle and not directly overhead. At some point when I was in one of my physics classes I could calculate that if I was given a certain angle but it's been too many years and I haven't had to do that since my physics class.