How ironic, seeming as re-learning the UI is a common criticism of Linux.

Yet I do agree. While my approach to Linux is probably quite different from yours, I have found that it allows me to build upon existing skills rather than learning new skills. To give you and idea of what I mean, I have been using the much maligned vi editor for nearly 20 years. (The editor itself even predates my birth.) Every year I get better at using vi, and I'm more than willing to use newer implementations of it to gain access to more powerful features. Even though I am using a different implementation today, the skills that I learned 20 years ago are still valid so I am becoming more effective at using the software. Since vi is entrenched in the Unix world I am also confident that this skill building will continue for decades to come. I can make similar claims for many utilities that come with Unix systems.

The other nice thing about Unix is its nearly universal nature. If I know how to use a userland feature on Linux, I can probably use it in OS X. It is also applicable to varying degrees on my Android and Kobo devices. Yes, there are going to be some changes (GNU vs. BSD vs. Busybox) but the basics are all there.