With my Samsung Galaxy S2's built in Update method, I updated my phone to Android 2.3.4 a week or so ago.
I'm happy to report that it was quite straightforward to do, and you don't have to do it via Kies at all, you simply do it from the settings section of the phone.
Here's a quick tutorial on how to go about it:
First, go to Settings and scroll down to the bottom:
At the bottom of the list, you'll see the option for "About phone" - go ahead and tap on that:
This shows you all the info of your phone, and at the top is the option to do a Software Update for your phone. Tapping on that one gives you:
From here, just hit Update at the top, and follow the on-screen instructions. That's unfortunately as far as my instructions can go, because I've already updated mine, and when I try it, I simply get a message telling me there are no current updates available.
Just note, the update does take several minutes to complete, and while the update is in progress, you won't be able to use the phone (make and receive calls) at all. Make sure your phone is charged before you do something like this...
Till next time!