I've had my sleep image disabled for over a year on my MBP with an aftermarket SSD. It hasn't affected me in the slightest, save for the additional 8GB on my drive.
AFAIK, the only time it could become a problem is when the battery reaches complete depletion, as the machine would be unable to restore the state it was in prior to shutdown.
Below are some Terminal commands relating to the sleep image.
To view sleep image size:
ls -lh /private/var/vm/sleepimage
To prevent the creation of the sleep image:
sudo pmset -a hibernatemode 0
To delete the sleep image (thus regaining HD space):
sudo rm /private/var/vm/sleepimage
I can confirm that the above commands work for both Lion and Mountain Lion.