I use two Operator...the Wheelsmith and the Park.
Both aren't too bad...and I often compare the two.
The Wheelsmith has horrible resolution...but is quicker and easier to use.
The Park has better resolution...but quite frankly is very big, bulky...slower to work with.
Thing I always do with both is wiggle a tad after spoke attachment BEFORE I do a reading. Both tend to read very high until they settle down after a slight wiggle. The Park is the worst offender. It will sometimes drop a whole whopping 20 kgf after a slight wiggle...and in doing so read more consistently and pretty much match what the Wheelsmith is reading.
Thing I really hate about the Park tool - is that I am very very afraid to drop the thing. It really does look and feel that flimsy in its construction.
Overall...I prefer the Wheelsmith. In the future, will probably go DT or FSA...and then have 3 to play with!
So far, they do the job.
=8-)