I have read around and found some people think it's theme related. That doesn't seem likely.
It's evident that the lag is not theme based based on a simple test. Minimizing, unminizing, and other menus open instantly while using the same effects and/or theme. I think that rules out the theme being the issue.
The other possibility is the read-speed of the hard drive when it executes the program. That means the work around would be to keep the menu app running in the background! That's probably really easy to do since it's a python app.