RT 4 experiences

For those who have installed testing versions of RT 4, what are your impressions? I’m deliberately not asking when it will be released since I know it will be released when it is ready.

I don’t yet have time to set up a test installation, but I’m hoping to free up time for that soon. In the mean time, I wanted to hear what people thought.

Is the interface the same new one from 3.8?

Does functionality change much?

When we went from 3.6 to 3.8, enough changed that we had to do some training and plan the rollout fairly carefully.

Can we slip 4.0 in without people noticing, or is the upgrade bigger than that?

Just general impressions, etc.