Many new MacBook Air users are complaining of slow wake from sleep times with the new Mid 2013 MacBook Air models. As it turns out the problem isn't new. It first manifested itself when the MacBook Pro with Retina Display was released in June 2012.
Erv Walter noticed the same problem with his MacBook Pro with Retina:
After opening the lid, it pretty instantly shows the password dialog box, but that UI is a lie. In reality, what is immediately shown is a screenshot of what the screen looked like when it went to sleep. The UI, although visible, is not functional for almost 10 seconds.
Walter discovered that the reason for the delay is Apple's new standby mode which is built into OS X to achieve longer battery life when MacBook Pros and Airs are sleeping, and he posted a terminal trick to change the default value. Apple notes that a fully charged MacBook can remain in standby for up to thirty days. The downside to the new standby mode is slightly longer wake times when you first open the clamshell.
According to Apple's knowledgebase article HT4392 ("Mac notebooks: About standby mode") affected models include all MacBook Pros with Retina displays and the MacBook Air Mid 2010 and later. Standby mode activates after just over an hour of regular sleep and the contents of RAM is written to the SSD then power to the hardware subsystems (i.e., RAM memory and the USB bus) turns off to increase the length of the standby.
If you're willing to trade off a little bit of extra standby time you can get faster wake from sleep times by extending the window of time that your MacBook remains in regular sleep mode. I extended mine from the standard hour to 24 hours and am quite pleased with the results.
Here's how to do it on your MacBook:
First, run the following pmset command with the -g flag (in Terminal) to see what your current sleep time is (in seconds):
pmset -g |grep standbydelay
Terminal will then display the time (in seconds) before the Mac enters standby. Make a note of what your default setting is in the event that you wish to revert).
4200 seconds (70 minutes) is the default for MacBook Air (your number may vary).
I changed the standby delay for my machine from 1 hour to 24 hours by running this command from a terminal window (86400 seconds = 24 hours):
sudo pmset -a standbydelay 86400
Using the sudo command requires admin privileges, so enter your root/account password and hit return. Changes require a log out/log in to take effect.