I could go into my reactions at length, but there's a ZDnet article that already did it for me. Go check it out. Smoothest upgrade ever. I'd only add a couple of things.
Know that your computer will restart several times. If you're on a laptop, keep it plugged in throughout. You'll think it's done, but then it will start installing again. Just let it be. Even when Mavericks finally comes up, the computer will continue to do some work in the background. Simply let it do what it wants to, without interruption. You'll know when it's done because your computer will fall asleep, as it always does when idle. Then you can play with it.
But there's more. After it's done, do Software Update again. There will be a few additions to install. And when all that is done, restart your computer manually. Then it's done.
As always, back up before you begin. And when the install is complete and you're happy, back up the new setup.
For me, the best thing about the new system is tagging. You just click on a filename in the title bar of an application, and add all the tags you want. Goodbye folders, hello tags. They should have done this long ago but I'm happy to have it today. Good luck with your install (but you won't need luck; it just works).