It seems that marijuana also has, very light, withdrawal symptoms. Not comparable to nicotine or cafeine, but still. Heavy users seem to feel a bit depressed and may have trouble falling asleep without.
I'm a moderate user myself, most days I'll take 1 'balloon' from my vaporizer using about 0.25 - 0.5 gram of (home grown) weed. Using this amount, I notice absolutely nothing when skipping use (e.g. when I go on vacation abroad for two weeks, not taking any weed): I look forward to go on vacation, but also have something to look out for when coming home :).
For me it is like computers or music: I can do without, but I'd rather not.