Putting a Mac notebook to sleep is taking progressively longer and longer as time goes by. The reason? We're all ordering notebooks with 2 to 4GB of RAM now, and by default, OS X writes the entire contents of memory to disk before going to sleep.
Since Apple is pretty good about force-sleeping the computer before the battery runs out entirely, it's actually very rare to run out of battery altogether. I think in the entire time I've been using Macs, the safe sleep function has only been necessary once — and that was when I changed an old worn out battery over to a new one.
Fortunately, you can disable safe sleep mode, by entering the following into the terminal:
sudo pmset -a hibernatemode 0
If you want safe sleep mode back, just change the '0' to a '3'.
Voila — your Mac will be back to the good old days of instant sleep.
There's also a preference pane that can do this called Smartsleep, which lets you select a nice middle-ground: only use safe sleep mode if the battery is running low at the time you sleep the notebook. For me, who is usually plugged into the power point, that's ideal!