In December we shared our early experiences with OS X Mavericks (10.9).
I noticed the right click on my Apple Magic Mouse was no longer working. Initially I thought it was something wrong with the mouse but when I booted into Windows using Boot Camp, the right click worked just fine. I had originally installed Mavericks as an upgrade to Mountain Lion (10.8).
I decided to perform a clean install and that resolved the right-click problem.
The trade-off was that I had to reinstall some things like my printers and scanner. Apple Software Update will automatically install necessary drivers when you add the printer or scanner. However my Canon scanner was old enough that the driver was not available from Apple. Canon also did not have a current driver, but I was able to copy some files from my backup of the Mountain Lion installation and partially restore the scanner drivers. With the aid of VueScan software, I can now scan again.
We also took a look at the updated iPhoto. I connected my iPhone and imported some new photos. The only difference we could see from the old iPhoto is that the location feature now uses the new Apple Maps included with OS X Mavericks.