I live in Grenoble, France - a very flat, medium size (150K people), city close to the Alps.
Since I’m 10 or so, I have always been a heavy user of b*cycles to ride in the city, back in the days this strange kind of 2-wheeled object still existed in my mind. 
It’s now around 6~7 years ago that I started using unicycles instead, for commuting downtown. From Monday to Friday, I ride to work, all the ride being in the city environment, and it takes just a few kilometers from where I live. But occasionally, I could ride much longer throughout the city - though never really more than ~10kms I would say.
I was riding a 29er the first couple of years, but have settled since then to a 36er (Qu-Ax then UDC then KH). I really find it to be the perfect way of moving around in the city: just fast enough, not that risky if you are careful enough (speed is lower than most bicycles anyway + vertical-ish position and elevation definitely helps to see the danger coming), so much fun to ride, and obviously enjoyed by most of the people watching you.
Well, I have also used my new 26" Guni for a little while as a tentative replacement for the 36er, but quickly came back to the 36er - finding it better suited after all to the road/city use, but also much more enjoyed by the people as well (the “big wheel” effect…).
On my 36" Muni, I have used 125mm cranks most of the time, went down to 102mm for some time, and now am presently using 110mm cranks - which I find a very good balance (in my environment) between “top speed / comfort” and “control”.
Outside of exceptions, I systematically use a backpack, because -for pretty obvious reasons I guess- I don’t like much holding something in my hands while riding.
Worth to be mentioned, I NEVER met anybody else on a unicycle in the city - even though that’s really a daily activity for me. Really, I don’t have the feeling that the unicycling sport is growing down here (unfortunately) - not at least as a way to commute. True also that I am not riding very often in the old part of the city, but rather outside of it, in the “suburbs”.
Once I arrive at work, I have access to showers, but decided to do it the simpler and more convenient way: I am basically only washing my top, and changing my t-shirt for a clean one. And -to tell you everything- I will use this new t-shirt the next day to come to work - in order to not wear 2 t-shirts a day but only one (yes I’m a lazy man ;-p).
Cheers, Pascal.