The killer feature for me is that you can patch the builtin apps. The WebOS OSS community is actually pretty cohesive and have their own market with a subcategory for system patches. You install it like any other app and it runs patch in the background, restart the phone and the patch is applied.
After owning an android device for a year, I've come to realize the only features I use are directions, web, mail, and Kindle. I regularly dislike/want one particular feature in these apps and feel that I can get them to work how I want if I can patch so I'll be switching over when I get a new phone.
I'm in the early access program and I've spent a couple weekends on it. Waiting on clarification on Enyo's licensing (i.e. can I use it as a baseline for cross platform apps) which has not been forthcoming before actually investing in the platform. I've been asking about Enyo licensing at events since January and nobody will say.