Push notifications are much better than receiving a text message and require a minimal number of clicks/taps
Setup was incredibly challenging without IT support
From a user perspective, I'm a fan given the push notification options.
I understand the need for dual authentication, especially when laptops are easily stolen, working for a global company where travel is a frequent, etc. It's a necessary evil, but Duo makes authentication rather simple - once it's set up.
Let's say you're prompted to change your password by your administrator or log out of your company's intranet. You'll be prompted to provide your password, and a Duo push notification will be sent to your device. Swipe to open the notification, and tap the green check mark. It's relatively easy, and much better than punching in a 6-digit code from a text (though you can go that way as well).
I appreciate the fact that Duo allows me to authenticate via both my work and my personal phone. If I don't have my work phone nearby, it's easy to log into Outlook web, authenticate via the same phone that's in my hand and view my meetings for the next day, for example.
The one thing I didn't like was setup. I traveled to another office the minute I started with my company, and found myself in a catch-22 where I couldn't set up Duo without my email and couldn't log into my email without Duo. The situation was easily resolved, but be aware that setting up Duo requires a bit of IT help and isn't completely self-serve.