I have JB on my Nexus 7 - IT IS GREAT!
There will not be as much of a learning curve to use JB as there was the GB to ICS transition. I expect it will be extremely smooth by comparison. The GUI doesn't change THAT much but the OS is SOOOOOO much smoother and faster. I especially like the search feature. I didn't realize what it was like until I asked the question "What was the closing price of 3M stock today" (expecting the same typed out response and web links) and it TOLD me very clearly what it was and linked me up with the DJI and several other sites almost instantly. (I think the same woman does the voice for Google and Siri.) JB search was so fast that when I laid the Nexus next to a iPhone 4 and asked the same question, Google came back so fast it messed up Siri. How cool is that?
I personally look forward to it just so that I don't have to switch back and forth all the time. I have to keep in mind though that my N7 is not a phone (but there are SMS apps that make it do everything else...) and that there may be some phone related issues that I haven't had to deal with.
