I fancy trying this again, but is there a full installer? Don't want to reboot and install 4 times!
Unfortunately, no. You can install DP4 and go from there... I had to do it yesterday and it was inconvenient having to reboot and install 4 times. On the plus side, I have really enjoyed using Mavericks and am very impressed with the enhancements!
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Will App Nap sleeps some of the apps he leaves open constantly but does not use, even though he is on mains power ?
App Nap reduces power consumption by completely suspending your apps execution when it meets certain criteria. This ensures that your app does not periodically wake up to do unnecessary work. An app is considered to be a candidate for sleep if:
It is not visibleif all of an apps windows are either hidden by other windows or minimized in a hidden dock, and the app is not in the foreground.
It is not audible.
It has not explicitly disabled automatic termination.
It has not taken any power management assertions.
When all of these conditions are met, OS X may put the app to sleep. While asleep, the app is placed on a scheduling queue that rarely gets actual time on the CPU.
The app wakes up automatically when the user brings the app to the foreground or when the app receives a Mach message or Apple event.
To support activities that should not be suspended, the NSProcessInfo class has three new methodsbeginActivityWithOptions:reason:, endActivity:, and performActivityWithOptions:reason:block:to tell OS X that your app is actively doing something important. These methods do two things:
Allow your app to temporarily suspend idle sleep, display sleep, sudden termination, and automatic termination for the duration of a particular operation
Allow your app to temporarily increase the scheduler timer precision while your app is performing latency-critical operations
-From Mac Developer Library - Pre-release