Very customizable (I like having number row always visible, and having long press for symbols on each letter).
Has gif support built in.
My biggest pain point is:
It auto corrects words that are spelled correctly to other words. I type "our" and it changes to "out", I recently typed "purpose" and it changed it to "purple". Autocorrect is awesome and necessary, but I hate that it corrects words to other words and not just typos. I wish I could find a keyboard that has the things I like without this annoyance.
I just like the custom keyboards, and it learns my mistakes when I swipe. I always carry 2 phones, so I was able to sync the 2nd phone so my swipes are already learned on that phone.
Also, there's a snow keyboard that collect snow at the bottom of the screen as you swipe.