Just bought GS3 (my first Android phone)...should I install CM10 or wait for official JB update

Life long iOS user here but I made the decision to give Android a shot, plus I got a smoking deal on a GS3 on Craigslist. My question is simple, should I go ahead and install CM10 or wait for the official JB update from Samsung?

One other question, are there any disadvantages (e.g., power consumption) to running an alternate launcher (e.g., Nova)?

So far, I'm really enjoying the device with the exception of the TouchWiz keyboard. I'm not sure if it's bad or am I just so used to the iOS keyboard.