I just rooted my Samsung Galaxy S and flashed MIUIv4 ICS 4.0.3 love!
still in beta though the ROM i used is from DrZ.

Installation guide ~ http://www.theandroidsoul.com/drz-miuiv4-beta-6-based-on-ice-cream-sandwich-for-galaxy-s-i9000/

Development thread ~ http://forum.xda-developers.com/showthread.php?t=1449156

Enjoy! Root at your own risk!