The USMower that my father runs on a KX 080 excavator has been nothing but problems (this is the second one with issues). The bearing casting has broken 3 times now with only 20 hours or so on the unit. The previous mower wore through the drum from the knives hitting it. That was on a Kubota 161.
The primary problem he has had with both was lack of dealer support, not sure how USMower is going to be to deal with direct, but he is going to find out Monday morning.