Take your pick.... Galaxy S II Original Android Development - xda-developers

Android Open Kang Project.... basically alternative vanilla builds based on AOSP, just like CM9. They differ in customisation features, menu layouts/content etc. See What is AOKP?! (and Features List) - AOKP - RootzWiki

Only the build date will reveal that. The "latest" released isn't necessarily the most recently-built so the version strings can be misleading. The most recent listed here is XWLP7, dated 3rd April.

 

Check out Slim if you haven't already.

Have been running it with neak and it's been great.

 

tried hydrog3n again just now, restoring nandroid of omega as we speak

4.0.3 is so much better than 4.0.4 by a long long way imo

 

It's not a 4.0.3/4.0.4 difference. Omega is a ROM based on Samsung sources, whereas hydrog3n is AOKP based. These cm9/aosp/aokp roms are packed with excellent features and take some getting used to. I didn't like them at first, having only a sammy background previously, but after a little perseverance, i now think they are great. However, I'm back on checkrom gb due to the scrolling and battery issues, but this is an ics problem, and not particular to these types of roms.
I've not tried a Sammy based ICS rom yet. I might give omega or andyx a try.