While I was hoping for support for broader package management (easily installing an arbitrary ARM deb package manually or from an arbitrary repository), I was impressed with the direction Ubuntu Touch is headed.
The premise of a unified desktop experience, from mobile devices to desktop computers, is very appealing. It might seem like a new spin on what Microsoft or Apple have done, but Canonical had some pretty original ideas and innovations, which they're working out. I loved the concept Canonical put forward regarding Ubuntu Touch, how one moment you could be using your Ubuntu Touch phone as a phone, and the next plug in a monitor/keyboard/mouse/dock and have a fully functional desktop environment.
As a developer, I like the toolchain for application development, which Canonical has provided. It makes it easy to develop an application for multiple platforms, conveniently providing for development using a number of technologies. I especially enjoy the support for Go.
Restricted package management. Difficulty of deployment onto the mobile device. Though, that is rapidly becoming a non-issue.
It was beneficial to me to have found a mobile operating system that is pleasing from a linux user's point of view. Currently, I do not use this to meet a particular need, but I certainly plan to in the future.