When I was in a psych class in high school, we had a (certified, of course) hypnotherapist come in and give us a demonstration of hypnosis, which is, in my experience, a lot like meditation, but with more focusing. It's really much different than what most people think it's like.
Hypnosis, as I was introduced to it, first involves concentrating as hard as possible on a single thing and convincing your mind that it is true --- in my class, we imagined a million balloons tied to our wrists. If you are suggestible enough, your arms will begin to rise on their own --- THIS IS VERY COOL WHEN IT WORKS!! Swinging a pocket watch is really ridiculous and old-fashioned, not to mention not terribly effective. This is nothing like that.
Also, it's not like you fall asleep --- you mostly feel kind of strange and drowsy and hazy, but at the same time still aware of your surroundings (unless you're suggested otherwise!). Additionally, you will probably not do things that you don't want to, because you are still in control (to a degree), and you will remember things! Hypnosis is an altered state in that you experience things differently, not in that you become some mindless slave to the hypnotist.
But my personal favorite part of hypnotism is that when you come out, you feel like you just woke up from a nap! It leaves you feeling relaxed and clear-headed (after you get over any grogginess). You could almost equate it to a state of transcendental meditation, and it may even be the same brain processes going on (I don't know). It certainly is a unique experience, but one that takes a bit of effort (for most people) since you have to focus so carefully.