Mainly using mine just for the fun of it. I enjoy having something to tinker with, and these little motors and the bikes themselves are relatively cheap which makes it more friendly on the budget.
If my Phantom continues to prove itself, and once I have my 110 ready to go I have considered using it for mild commuter duty for going to some classes I am taking or maybe even going to work when I have a random wild hair up my butt. The only reason I don't consider using it more for commuter purposes is the fact that I get off work at 11:30pm, and I don't have any lights setup. Plus, I have a 250cc dual sport that fits the role better.
I have considered one of the more high powered e-bikes like the Talaria Sting to use strictly for work duty when it isn't winter outside, but the entry price to those bikes is pretty steep, and the upgrades are as well.