I've never used one but have read magazine comparisons between several brands. The harbor freight are less precise ( I want to say. +- 6%). Worth the purchase for your average items just not the super critical, low torque stuff
I broke several water pump bolts off in my block using a Harbor Freight torque wrench. Like Tonka says, I wouldn't trust it for the sensitive stuff, and the stuff that isn't sensitive doesn't really need a torque wrench anyway.