I've talked about this a lot the past three or so weeks since I got my Honor 8. To be short, emui offers a lot of useful software enhancements (gestures, optional battery optimization, caller blocking etc) and customizations (dark themes, custom nav bars, app theming, etc) .
I really can't tell you every reason why I like emui here, but I can tell you I really think it's great. My past two android phones were a nexus 4, and a 2nd gen moto x. So I really like the stock android look and feel. Out of the box, emui looks funny. But it doesn't take long to make it your own. I'm currently using a dark emui theme and action launcher- it's awesome. I couldn't customize my previous phones like this without a custom rom.
Notifications could use a bit of work. I'd prefer the stock Android shade look/functionality, but this hasn't been an issue for me-at all. It works fine, it's just not what I've been accustomed to. I did not like huawei launcher, or the built in lock screen. Both of these are super easy to replace within the play store, and this doesn't interfere with other functions.
There are a couple YouTube videos showing how emui themes work, check them out. I think I learned more about the os and how it looks from these than the corporate reviews. Also, take a look at the screen shot thread.
It's not a deal breaker, not even close.