Why should I NOT update to Mavericks? I'm not really looking for a single correct answer. I'm just looking for some input regarding the inevitable "gotchas" Apple seems to sneak into every major OS X release that screw over a select handful of people before they have time to resolve whatever feature or app got removed in any given release. I want to know about anything at all; I'm a developer, so even lower-level system tweaks and restrictions have an effect on me.
You (or anyone else) should not upgrade if you don't have a good backup, a good idea how or why it will make your life easier and you don't have a list of software that you need to work so you can check at your workflow won't get ruined or at lease slowed / disrupted.