Maybe it's just my playing style, but I have had nothing but bad luck with these guys.
These are models. Plastic, and will easily break under a beating (don't even drop them off the table to a wood floor). They're excellently-sculpted, although one of the guys' faces (the one with the hood up but pulled back w/spear) looks retarded. :-)
As for gameplay quality...I've only EVER seen Rangers used in at LEAST blocks of 3 companies. Usually, more. The first time I ever played War of the Ring was during a mega-battle event. I had The Betrayer, 4 companies shield mordor orcs, 3 companies orc archers, and 2 catapults. I was creamed by Aragorn, 1 company of Minis Tirith warriors, and SIX stinkin companies of Rangers! Holy cow, these guys are annoying at range! Lost almost my entire force to them alone.
Likewise, using them is ridiculously easy. Just plunk them down and shoot anything that gets near. I've rarely had to move them at all once the game starts.
Sooo....all that to say they seem rather overpowered. A bit like the Space Marines in 40k: they do EVERYTHING well, and the few things they don't (like move quickly) don't matter for their roll. They ARE THE vanilla 'unit' of War of the Ring.
So. Avoid like the plague if playing against them. If using them, have no fear, you've already won.