Some time ago, I converted both mine and my wife's user accounts to OS X Server network accounts. The advantage of this is that our home directories are stored on an OS X Server as portable home directories (PHD). Everything was working great under Mountain Lion and when Mavericks was released a this past week, I was anticipating a smooth transition.
In the midst of it all, my wife's hard drive encountered some S.M.A.R.T. errors and couldn't install Mavericks. Because her account was a mobile network account, she was able to sit down at my Mac mini, login with her usual username and password and everything started to sync over from the server. Of course, it was a slow process, since I outsourced my server to a datacenter, but the ability to have an off-site repository for our data that is highly secure definitely helps me sleep at night.
I wasn't so lucky - if you want to call not having to replace your hard drive due to S.M.A.R.T. errors lucky.
The initial upgrade to Mavericks was smooth and surprisingly only took around 20 minutes to download. I say surprisingly because normally my connection at home doesn't sustain a constant download rate for long. After the installation was complete, I restarted my MacBook Pro only to come to a login screen that wouldn't accept my username or password. It appeared that whatever mojo was working behind the scenes of upgrading Mountain Lion fragged my ability to bind properly with OS X Server. My only recourse was to back up my files manually from the existing home directory (luckily I keep a master administrator account on all machines in the network) on to a portable hard drive I keep for such emergencies. Then it was time to reinstall Mavericks from scratch.
I took the time to completely wipe the hard drive with a new partition scheme. After the re-installation was complete, I again arrived at the login screen and this time - after a few seconds of edge-of-your-seat anticipation, I was greeted with the familiar dialog box asking if I wanted to create a mobile user directory on my machine. "Success", I cried mentally.
It's good to know that if disaster ever strikes - I need to reinstall an OS, replace a hard drive, etc - most of my time will be spent making the repair, not transferring data back and forth between server and client.