Honestly, first and foremost for me is the wave feature. I love the deployment for all practical applications.
I like the fact that I can get the 154CM steel back to shaving sharp pretty easily (& much more easily than some comparable 'super-steels'.
I love the feel of most of the handles in my hand. For me, some of my Emersons are the most comfortable, secure folding knife handles I have ever felt. I just can't decide between my Commander or my Roadhouse!
I am ridiculously drawn to the stonewash/satin finishes on various blade grinds. The work is stunning and the choice is fantastic.
I have grown to love the overall utilitarian looks.
Could not be happier and I can honestly say that since I bought my first Commander, I have never not carried an Emerson. On occasions, I will add another knife (typically a SAK Pioneer, but sometimes a Spyderco slicer like the Caly series) - but I always have an Emerson (or two) on me now.
Go ahead call me a fan-boy but I have actually tried lots of knives in real use (Spyderco, ZT, Fallkniven, Benchmade, DPx, Hogue, etc.) and I'm extraordinarily happy with my Emersons as my go-to folders...
Ben