The announcement of Mavericks during the WWDC in June 2013 did not receive as much attention as iOS7, for obvious reason that there are more iOS devices out there than OSX.
Anyway, I have installed the Mavericks on my MacBook Pro with Retina Display. The installation was simple and fast. No fuss nor whatsoever.
I have the Mac up and running in less than an hour. During that time, I had my MacBook Air 11 with me for work. So pretty much I was working and left the Mac to run on its own.
The interface is pretty much the same as before, since Tiger, I think. I started using Mac when it was at Leopard.
I like Snow Leopard, with better stability, however I hated Lion, and then like Mountain Lion.
For Mavericks, I believe there will be some flaws. I am to have found some later.
As for Mail, it has seriously stopped the innovation since Lion. Kind of sad. I hate Mail, so opt for Sparrow and AirMail for now.
I like the Dock which now follows whichever the active screen is.
For Menu Bar, it appears on all the screens now. I am using 3 displays while at work – 2 external monitors and display from Mac.
More to come.