Wow, lots of different stories here. I've been using Ambien on and off for years, so I'll recount a few tales.
Firstly, snorting 20mg of non-CR Ambien has knocked me out like a light. Bit of a burn but not much. 10-15 minutes later, blammo. Taking the same amount orally just put me to sleep after 30-60 minutes. Anyway, blammo, can't remember a thing, and there are times I did things during the blackout. Once this went very wrong, as while I was blacked out I apparently decided to take a bunch of 8mg hydromorphone. I probably snorted those too; I only recall waking up in the ER later.
Since then, I won't mess with ambien unless there's nothing lying around I might get into. I hear the horror stories of people driving and am thankful I never did that.
Ambien CR 12.5mg is a far different beast. It doesn't burn as much. Snorting one or two might make me a little woozy but not much, and it doesn't make me sleepy. I have never blacked out on it unless I combined it with booze (much like benzos, a bad idea for me), or a strong opiate like hydromorphone. I don't recommend combining those unless you really know what you're doing.
Recently I did try plugging 2 12.5mg CRs and I can't recall anything that happened until the next morning. Apparently I just went to sleep, and I slept well. Tried that again a few days later, and nothing much happened. Unless I really want a fast nap I won't bother trying that again, and I'm not about to try smoking or IV'ing the stuff.
I have constant sleep problems; even on a mammoth dose of Seroquel (I take 800mg at night), it doesn't put me out, but taking an Ambien 12.5 CR usually finishes me off. I sometimes chew and swallow one if I want to get to sleep faster, but usually I just take it as directed.
Ambien can be fun to mess around with, until you black out and have no fucking idea what you've done. It's landed me in the ER, and a few times I've had tales of stupid shit I've done recounted; I've been embarrassed at the very least. I see that it doesn't affect some of you and that's cool, but for the rest, be careful when you try it out. Generally I find I just use it for what it was intended. Tonight, I'll snort a little, after I hide my keys and my cellphone...