I happen to have such a phone, and was initially elated to learn that my upgrade had finally come! I clicked "install" without thinking and immediately went back to sleep because I've got a cold I'm trying to beat.
Anyway. When my phone and I had both rebooted, I picked it up and starting futzing around with it.
The new keyboard is a bummer and it doesn't recognize dictionary words. Seriously "today" is autocorrected to "Today" because for some reason the phone can't figure out where the dictionary is. Additionally, the keys are all smaller now - so typing is even more of a pain than it used to be.
On the bright side, the stock keyboard has a new cursor system that lets you edit mistyped words MUCH easier than the Froyo keyboard.
I am told the workaround (not fix) for these keyboard problems is to download another free keyboard from the App Market.
The major bummer about this update is that it did not fix the issue where my Mac (or any other computer) fails to recognize the phone via USB connection. I had this when I was running Froyo and I've got it still on Gingerbread - except now, the phone refuses to charge as well! This is a problem I had on and off for a while in April and early May - though eventually it started charging just fine again. Now it won't charge from the wall, the computer, or from my super-energized-mind-waves. Fail.
I've tried rebooting and resetting it - neither worked and I have read that even a full reset of the phone has not fixed this issue for other frustrated Optimus S users.
My hope is that Sprint/LG will get their hands on another update and send it out expediently, otherwise my phone very quickly becomes a paperweight and I will have to do all my phone calls/texting from Google Voice. This works just fine as long as I don't leave my house...
Overall, the following illustration just about sums up how my phone feels about the Gingerbread 2.2.3 update:
