So, if you're a Samsung Galaxy S II owner just waiting to get your mitts on Android 4.0 Ice Cream Sandwich (remember, you don't get it as an OTA update, but via Kies on your computer!), then this *may* make useful reading: Samsung has put together a handy little PDF document explaining the differences between Gingerbread and ICS to help that transition.
We use the word *may* above because if you're reading this site, chances are you will have spent months being taught about Ice Cream Sandwich and what to expect and won't necessarily be needing a lesson in how to use it. But it's bound to come in handy for some people, like Samsung reps and mobile shop workers, judging by the way it is laid out.
For those people who do it the proper way (ie. install it as Samsung would rather, not by sticking a custom ROM on), the updates have begun arriving, in line with the promised March 19th commencement date. That's primarily for Sim-Free units, though the likes of 3 have also begun their delivery. Orange users, meanwhile, may have to wait a little longer due to a delay which they've tweeted about.
Best way to do it is plug your phone into your computer and give it a whirl. And don't forget your handy little guide too!