I do this too, just make sure they aren't too close to the hives, or the bees will go looking for other easy pickings
They do get aggressive when cleaning the cappings up, and I've been stung if I get too close. And it attracts all of the neighborhood wasps, hornets, yellowjackets, vespas, and other unsavory characters to your area.
I think I decided I'll do it earlier in the summer when there is a flow on, but during a dearth and in the fall...it is just too many flying bugs with stinger butts for me to bother with.
You can do the same thing inside of a hive, just stick it on the top bars with a box overtop and make sure that there aren't any easy entrances, and they will clean it up good without the crazy bees flying around.