No experience with renting from them, so can't help you on that part.
I do have experience with them in taking care of some damage done to my powerchair on a flight in. All I can say is

. They worked with me on which time would fit me for them to come around, reconfirmed that by calling in a short time before. I've got a chair that has basically been totally rebuild from the ground to fit my needs and has things on there that tend to be nonstandard.
Sure enough, the cushion for my back was punctured (I've got an aircushion) and thus not possible for me to sit in the chair. It was a bit of a catch 22 at first. I've got a Permobil chair and the cushion (actually a baby cribs mattrass

) for my backrest is from Roho. Apparently in the US the two of them have got an agreement where it results in Roho not delivering any of their products to Permobil users but requiring them to go through Permobil. Nice and peachy but Permobil did not have the cushion I needed. Roho did, but didn't want to deliver to me/Florida Mobility. They wanted us to have Permobil order it, sent it to Permobil, have Permobil sent it to us etc.
Nuts and it would mean a couple of days extra for me without being able to use my chair (and not being able to use a rental because of needing such specific stuff). It took a lot of talking and keeping at it, but eventually FM got the green light and Roho agreed to ship us the cushion directly. Then FM basically would not back down until Roho agreed to ship it a certain way which would result in us having that cushion the next morning instead of having to wait a couple of more days (standard way of shipping would take longer and that day being a friday with the weekend coming up).
The work itself didn't take much time for FM to do. But before they could do that? They literally were making calls for over an hour of pure phonetime between Roho, Permobil, 3way calls between them and having me listening in most of the times. They made sure I'ld get what I needed a.s.a.p. instead of just going

"can't be changed, you'll get your fix eventually, this is what we get paid for by the airline, take it or leave it". All this legwork was done by the owner (can't remember his name right now, oops).
In the end they started working on this on friday afternoon and on saterday around noon I had my powerchair back in a working state.

They could've all too easily not gone the extra way and waited for the "standard" way of operation. They didn't. They could've waited for our backup to pay out (I knew this cushion isn't a standard and expected some problems, so my own dealer got a new one out to my dad. He would've delivered it to the airport that saterday morning, where the airline would've had it flown in and delivered to us on sunday evening). Again; they didn't. They promised to get my up and going a.s.a.p. and they came through on that promis.
Totally of no help with your rental question, but perhaps it helps out a bit if there are any things you wonder about in case you find you'ld need any technical help for the rental. (I know I personally take this things into accound, so that's why I blabbered on about it)
Have a great time at Universal!