Using the UTM for over 2 years now, and still like it very much. The setup is easy and within 15 minutes your up and running. Web GUI has everything you need, all grouped together (some things aren't that logical, but as with the latest updates this is improving a bit).
For me this are the top features i like about the UTM;
-- It's relative light weight, so easy to run on some older hardware you have laying around. But I don't have any problems with newer more "enterprise" hardware as well.
-- A ton of functions (like a UTM should have). Everything from simple Firewall & NAT to Email (encryption) & advanced routing protocols
-- Easy and nice Web UI (speaking as a someone who normally skips products with a GUI), it contains all the information you need.
-- The Live log is just great!
-- The ability to "map" hosts, users, groups etc. is very handy. This way you just have to change your settings in one place in stead of reconfiguring everything where you use that particular host.
-- LDAP/AD integration is essential for enterprise usage, and works as expected.
-- The CLI, it's just a regular Bash shell but with minimal packages. There also isn't a way to install your own sinds there is no package manager and build software is missing. I think they can improve here a lot. For instance adding a package manager so we can install software on or one but preferable add a "Cisco-like" CLI, so that we can manage all the functions that are in the Web UI with a sophos-*** command.
-- Some minor inconsistency in the menus, but as i mentioned already, this is improving and not that big of a problem.