Dann Berg covers more than just the main cosmetic differences in Apple’s OS X Mavericks for Mac. I installed it on four Macs with zero problems; two of the Macs are over five years old.
Everyone should upgrade to Mavericks… There’s no good reason not to — it’s free, it’s faster, it has a few new and improved apps. You’ll probably see your battery life improve after a few days. But don’t expect a radical rethinking of what a desktop computer can or should be — that job seems destined for a future version of iOS.
Easiest upgrade ever.