Used them many times over the years...last time we used them it was horrid with us needing 3 different strollers delivered and being yelled at by the owner and told I was not being honest about what one of his workers told me. In thier defense, they did refund the entire fee we had paid but I had a lot of wasted time picking up and dropping off strollers at bell services. But we have also used them many times previously without issue- maybe it was just a "Murphys Law" kind of week with the strollers they kept giving me.
Since that experience we have used Orlando Stroller rental which is also a Disney preferred rental company and have had great service with them.
We used Apple Scooters and had a great experience 4 years ago. The stroller we got at first was busted, and they had a new one ready within 30 minutes.
Their scooters do not seem to get good reviews though, so maybe their service is not what it once was?
We used Kingdom on our last trip. Had a great experience. We rented a stroller and a full size crib. We did a split stay and they even transferred the crib from one resort to the other for free. It was a very easy process and fairly priced in our opinion.