Vim Scrolling Slowly
Solution 1:
:set lazyredraw
will buffer screen updates instead of updating all the time. I generally enable it when I'm doing a complex macro playback. Might help you here.
Solution 2:
Have you tried the 'ttyfast' option? See:
:help 'ttyfast'
for help, and:
:set ttyfast
to enable it.
Also, what version are you using? And have you tried this with no customizations to see if something you've set is interfering?
Run it like this to omit any of your vimrc settings and plugins:
vim -u NONE
EDIT: If removal of customizations fixes it. Remove things iteratively until the behavior returns. Start by narrowing it down to either a vimrc problem or to plugins.