A ROM that is based on Android OS 4.0.3 (Ice Cream Sandwich) has been found for the Samsung Galaxy SII. The I9100XXLPB ROM is apparently stable enough for daily usage without any problems.
Unlike the version of Android ICS found in the Samsung Galaxy Nexus, which is stock, this version includes the TouchWiz UI on top of Android 4.0.3.
The source of the ROM also claims that it makes the battery performance much better.
If you'd like to flash this ROM on your Galaxy SII then simply download it from the link below and you're good to go, or you could wait a few weeks for its 'official' release.
As usual we do not hold any responsibilities that come to your device while trying to root and/or flash a ROM, and you must proceed at your own risk.