What I dislike about the overview is that it takes over the whole screen and also feels a little sluggish. I like the ulauncher loads really quickly and on top of the current UI, blocking virtually nothing from view. Also I like having a few bells and whistles that ulauncher has, like the ability to type a quick math problem and it functions like a basic calculator.

edit: I just realized that I'm mislabeling the thing I dislike. It's the "show all applications" feature in reality. I use overview a lot just to keep track of what I have open, and I like it, but it serves a different purpose than what I want, which is just a very quick and unobtrusive way to launch an app not on the dock.