Not particularly. There are no large seeds or pokey things. They do drop their leaves in the fall, and the branches tend to be somewhat weak, so you end up with lots of branch tips. But generally it is all minor and mow-able.

all deciduous trees are messy ... if you define the term.. perhaps you will get better answers ... ken

I would not want these trees anywhere near a pool or patio. They shed rather copious amounts of little catkins in the spring, then their leaves in the fall. Aphids can be a real nuisance, too, dropping sticky honey dew everywhere, black sooty mold following shortly.

Also, they develop surface roots comparable to a maple.

They are always shedding something, often small branches. I wouldn't plant one again.