To confirm that you're in Deep Sleep mode, open Terminal and type
pmset -g | grep hibernatemode
The output should be
hibernatemode 3, with the 3 indicating that you're in Deep Sleep mode. This is useful if you're putting your computer to sleep and you're low on battery—if your battery dies in sleep, your session isn't lost. But you get that 3–5 second delay, which can be annoying when everything else is blazing fast.
If you're like me and have the battery charged most of the time (keep it plugged in 90% of the time—it's the charge cycles that kills your battery, much more than any debatable effects of overcharging. Use the battery 10% of the time to keep the electrons flowing), you can disable Deep Sleep and get rid of the delay.
sudo pmset -a hibernatemode 0 in Terminal. It'll prompt you for an admin password. Type it in (note that it won't show up when you're typing, but it is being entered) and hit Return, and you'll have no delay when waking up. You'll also recover as much disk space as you have RAM, and those 8GBs or 16GBs are significant, especially if you're on a 256GB SSD.
Note that I've had occasional issues when waking with the recent SMC update (black screen and nothing happens until reboot), but even with a reboot you don't loose your session.