I have one of these ARS-1 colonies.  I noticed, too, that they are generally
not agressive -- except when removing honey supers!
 
I also noticed immediately that they were light propolisers -- however, they
more than made up for this by waxing everything together.  They built comb
between most frames, and even between top & bottom frames, making it
impossible to remove top brood box without tearing up honey and brood comb --
this, of course, upset their otherwise gently disposition.
 
The biggest factor, though, was their honey production.  They built up
extremely quickly from a 3-pound package the first week in April, and gave me
75 pounds of honey in June, with another 60 pounds or so in the fall (after
swarming).
 
Eugene Makovec
Kirkwood, MO