(I've gotten a couple of questions of 'how do I close a window in Infiniti?' which indicates folks are using the older, buggier version that cads posted here ages ago. I snagged the new one from him a while back and it's much better.)
This version still has lag, but like with all UI's, when it gets bad you can just reload it (you don't have to log) -- just go to options and load it again.
Here's a low-rez image of how I have it configured (apple cinema 22"):
If you don't like the spell icons on this or any other UI:
In the directory Everquest/Game/uifiles/(your UI name), there are two files, gemicons01.tga and gemicons02.tga, and 5 files, spells01.tg through spells05.tga, that you want to delete or replace.
I'm not sure which set I uploaded with that url (it may be "none"). If it's the new infinity ones and you hate them as much as I do, you can either delete those 7 files to get the original EQ icons or snag the ones from the originial infinity: http://www.frivolity.com/eq/ui-spell-icons.zip