I'm blown away by how great OmniROM is. With the Franco kernel, ART, and the latest OmniROM build my Nexus 5 boots in less than 10 seconds. Everything is faster and more fluid. I don't like stock 4.4 because I can't use Quick Toggles, but OmniROM is just the right amount of customization for my purposes.
Now, about that Multi-Window
(kidding, I know it's on the way)