VIM was very laggy for me after when I dialed my key repeat up. I know you're not supposed to but I sometimes just want to hold down j and scroll

When I would do this it would keep scrolling another 3-5 seconds after I let off the key.

Did some research and leared two very useful profileing tools built into VIM

:profile start profile.log
:profile func *
:profile file *
" At this point do slow actions
:profile pause
:noautocmd qall!

This will let you track down plugins that are causing performance problems

And sometimes your problem is syntax highlighting (mine was)

:syntime on

:syntime report