This of course hinges on how often "occasionally" is. Your body can easily get used to these pills and then you are up shit creek.

The following is from a medical website:

Common side effects of prescription sleeping pills such as Lunesta, Sonata, Ambien, Rozerem, and Halcion may include:

Burning or tingling in the hands, arms, feet, or legs
Changes in appetite
Constipation
Diarrhea
Difficulty keeping balance
Dizziness
Daytime drowsiness
Dry mouth or throat
Gas
Headache
Heartburn
Impairment the next day
Mental slowing or problems with attention or memory
Stomach pain or tenderness
Uncontrollable shaking of a part of the body
Unusual dreams
Weakness