I have one of the 'old' SS10x42's, circa 1998 or so (back when they cost a bit more than they do now). Thing is a tank. This winter I picked up a 16x model, because as Nate mentioned, 10x sometimes just isn't enough for little targets at longer ranges. Bill Wylde was kind enough to answer my emails about the 20x models; apparently he's used them w/ some success in Canadian Long Range matches and had no problems. Unfortunately by the time he answered, I'd already pulled the trigger on a 16x model. It seems to be as nice as the 10x model so far.
One thing I'd recommend based on my experiences: pull the turret caps off, clean the little O-rings inside, relube them w/ some O-ring grease (hardware or auto store should have some) and put the turrets back on. Repeat about once a year or as needed. Some people recommend just tossing the O-rings altogether (unless you plan on fording rivers and braving sandstorms w/ your rig), but on mine the turrets are almost too easy to turn w/o the friction of the O-rings.
HTH,
Monte