This is very exciting moment for me and I hope i'm welcome into this new family.
Here i want to share some experience as a newbie. I just bought my TF300T (blue) yesterday and it came with ICS 4.0.3.
It was smooth, zero lag and amazing when it was out of the box. Then i went back home and downloaded some apps and meanwhile upgraded it to Jellybean.
After everything was finished, the tab boot as usual but now the feeling was different. There was obvious stuttering and lag in any apps even at the homescreen.
I was sad and frustated on updating to jellybean. But then on the next morning, i did 'factory data reset', and everything is ok! The smoothness returned and much better than ICS. i was glad i did it and now i can't be happier than before.
I'm not yet root my transformers as to preserve warranty. The transformer is the best.tablet.ever!
St from my ASUS Transformer Pad TF300T using xda app-developers app