I’m not having a good experience with Mavericks on my 2008 iMac. I think the upgrade messed up my keychain in some way. Mail, Contacts and Calendar (my Google account) no longer sync — I’m constantly prompted to enter passwords over and over again. Removing the account and adding them back doesn't resolve the issue. Since my contacts and calendar are hosted by Google I don’t have access to them locally.
Facebook, Twitter, Flickr integration are also not working. I've removed them from the "Internet Accounts" panel in System Settings but the system won't let me add them back.
The iCloud Keychain won’t activate at all. I get an error message that my Mac failed to contact the iCloud server. Sigh!
What's annoying is that everything works fine from my wife's 2013 MacBook Air. I don't have any problems using any of the new features from my account on that MacBook.
In the mean time, I have switched to using AirMail and I may also switch my contact over to Cobook. AirMail takes a while to start-up but once it gets going it does a great job. I especially like that I can attach documents directly from cloud services like Dropbox and Google Drive. Cobook also has an iOS version. I like that close integration.
Anyone else having OS X 10.9 issues?