Well, I've fitted my Crayford to the Dob last night, and it's sweet. Bit of backlash with this one too, so it seems you'll get that with most of these units. But it's lightyears ahead of my R&P. Well worth the small investment. Handles big 2" barlow and nearly a kg of Stratus eyepiece without even breaking a sweat. The bit of backlash is only in the shaft and not the barrel, so there is no image shift.
The Crayford on the ED80 is a lot smoother with a much lighter touch and more sensitive tension adjustment. And when you get the tension right, there is no backlash. I thought that would have been a bottom end cheapie too... Maybe Synta make better focusers than GSO, or maybe refractor focusers are easier to make...
But I don't think I'll be buying any $400 focusers anytime soon; not till I have a $4000 telescope to put it on anyway.