Is Menu-minipanels reliable to make a mega menu I'm going to implement a mega menu in my site and am considering the Menu Minipanels module...

Has anyone tried it? Did you find it easy to use/customize?

What about performance? Panels is often quite a heavy module.
Menu Minipanels looks like a good choice.

An alternative you might want to try for a simple 'mega menu' is the Mega Menus module. Worked well for me, once I had my settings and CSS sorted out. See also this answer for lots more mega menu options...

Finally, regarding performance, since Menu Minipanels uses Panels you will have full control over caching of individual panes within it. The performance burden can therefore be significantly reduced.