People have been running Mango beta on their phones, they seem to run well even when it's not optimised for the phone's hardware. I was even tempted to try it myself. But while reading up on it, it seemed a hassle to restore no-do once you installed the Mango beta. I've decided to be patient instead
I did have the first Mango Beta 7661 or whatever, and it was quite sluggish.
When I bought my phone, I instantly threw Mango on it. So I don't know how NoDo was compared to Mango Beta's.
But I have been reading conflicting reports that some have been able to go to 7712 to 7720 and some people had to go back to the version that shipped with their phone and then make their way though the updates. TBH. I'll just wait until Samsung releases it. IIRC, there is nothing in 7720 that isn't in 7712.