If you use AppleScript applets to interact with UI elements, you may quickly find out that in Mavericks all seems to be broken. Every run results in System Preferences being opened to the pane that used to control UI Element Scripting, and finding the new controls in Security & Privacy -> Privacy -> Accessibility seems to have no effect.
This is a result of Mavericks splitting UI control authorization into per-app settings, combined with the Lion feature of remembering what windows an app had open when it was last closed.
Mavericks recognizes the app uniquely only as long as the app doesn't change.
WindowState information is stored in the app if you have permissions to modify it.
These two features end up caught in a fight.
The following Terminal command will prevent this by passing ownership of the applet to root and blocking you from editing it without authenticating.
Mavericks now considers each monitor a "Space". As a result, apps launch and have their menu bar in whichever monitor they were launched from. However, it's easy to assign apps to each monitor. Here's how:
First, you need to create an additional space in Mission Control. You can add it to either monitor.
Having done that, then when you right-click on an app in the Dock, you will see the option to assign the app to All Desktops, Desktop on Display 1, Desktop on Display 2.
If you are a heavy user of Spaces with multiple displays, then you have likely found that the new "full screen improvements" in Mavericks are a giant leap backwards. To get the old behavior back, just go to Mission Control in the System Preferences and uncheck the box labeled "Displays have separate Spaces."
Apple changed the looks of Notes.app in Mavericks and it is now mostly white with a light yellow paper texture as the note background. Turns out the texture is a TIFF file you can easily edit with any image editing app.
Quit Notes.app. Go to /Applications/Notes.app/Contents/Resources. Copy paper.tiff file to your desktop. Make another copy and save it as a backup to a safe place. Open Desktop/paper.tiff to Photoshop or some other image editing app. Use your creativity. After saving, drag the file back from desktop to /Applications/Notes.app/Contents/Resources.
I changed mine to a bit more saturated and removed the texture. Looks like a Post-It note.
Looks like Mavericks 10.9 has changed the behavior for adding application/document shortcuts to the Finder toolbar.
Where before you could simply drag any icon up to the Finder toolbar and hold it there for a second to add it, you now need to first hold down Option+Command and then start dragging the desired icon to the toolbar.
You can still remove the icons the same way as before: holding down Command, dragging the icon away from the toolbar and then releasing.
Finally after updating to Mavericks I thought I'd have another crack at changing the resolution of my headless Mac mini without using the VGA adapter hack. It is now much easier, as long as you know the trick to it.
First off you need an app to change the screen resolution (scrutil no longer worked for me so I downloaded Display Menu (free) from the Mac App Store).
After changing the display resolution my VNC/Screen Sharing sessions kept blacking out and I couldn't see anything so I fired up SSH and killed the screen sharing agent (killall ScreensharingAgent) and bam finally my remote screen lit up at my specified resolution (2560x1440). However my Dock was still in the middle of the screen (and killing the Dock seems to reset the resolution), so just right clicking the dock and changing its location made it fix itself up :)
Starting with OS X 10.8 Mountain Lion, your Mac could take dictation. But, just as with the dictation feature on iOS, the OS X incarnation required an Internet connection, couldn't show its progress while you spoke, and could only listen for about 30 seconds at a time.
That all changes with a single checkbox in Mavericks (OS X 10.9). Fire up System Preferences and click on the Dictation & Speech pane. There, you'll find a checkbox for Use Enhanced Dictation. The first time you check it, you'll need to wait out a hefty download (between 700 and 800 megabytes), but once you're done, you can dictate a lot more freely.
Now, transcription happens on your Mac, not Apple's servers. And you can see the transcription appear as you speak, in real-time. In fact, the cursor remains active too; if you see a mistake, you can click around (without speaking) to make your edits, put the cursor back where it needs to be, and start talking again. Unfortunately, however, Mavericks doesn't offer any ability to use speech-based editing tricks: If you say "delete that," Mavericks types "delete that."
New in Mavericks, Notification Center banners for reminders include a Snooze button. But that button, which removes the reminder and brings it up again ten minutes later, offers more customization than is immediately apparently.
Click and hold on the Snooze button to bring up a drop down menu with snooze times ranging from minutes to hours to days to weeks.
There are many hints here and on the net involving changing user defaults by running defaults write or directly editing the .plist files in Library/Preferences. Until 10.9, restarting the program was enough to apply the new defaults.
Since OS X Mavericks, the defaults system is caching the preferences system-wide (i.e. not in the application's process!) to improve performance of the user defaults API. If you use the defaults command, you are fine, since it appears to use the normal user defaults API.
On the other hand, if you edit a preference .plist file with a text or plist editor (even the one included with the most recent Xcode 5 preview), the cache will not be flushed and even after restarting the program in question, it will retain the old preferences.
The API documentation states that the cache is synchronized with the on-disk plist file contents periodically, but does not indicate how often, let alone how to flush the cache manually.
Logging out and back in appears to flush the user defauts cache, but other than that, the defaults command is currently the only way to reliably change preferences without waiting for the timeout.