Dave Kover the well known developer of many Launcher themes tweeted out a little tidbit of news that I had somehow missed.
"dave kover @davekover
No blogs have covered Apex adding theme support. I figured that'd be noteworthy given it's the first ICS-based launcher to do so."
He is right this is pretty exciting news! Apex launcher is the first ICS-based launcher to support themeing, and there are already a few themes on the market that will work with Apex. The screenshots above are just a few examples of what is already available in the Play Store! Apex has quickly become one of my favorite launchers, because it is simple, clean, and blazing fast. Add to all of that the ability to theme and i think we have a sure winner! It won't be long until we see a slew of Jelly Bean themes for this and other ICS launchers.
Apparently to update your Apex launcher just go to Apex settings, then about, then auto check for updates then click beta, then select check for update now! This should update you to the latest version with theme support!
As you notice in the update method it is under "Beta" so that should be noted as well.
Grab the Apex launcher here