Those Z-drugs are strange beasts in my experience.
I've been tried on all three of the current ones, zolpidem was just.....fucked up. Made me trip. I only intended to check my email, read a bit before going to bed, but instead, seemingly stayed up for ages on MSN, after it had started working without my really realizing it masking no sense whatsoever.
Burned one would know better than I would though, as I don't remember a damn thing.
Zopiclone does something similar, but a lot less extreme. Mainly just hearing strange noises out of the blue, as I was half asleep.
The other one, zaleplon was just rubbish, ultrashort-acting, and far, far too weak to even notice.
Today, taken some of them, some I only take later though. Had a nice long lie-in, thanks to the stuff I take to stop myoclonus/seizure stuff from happening, being a damn strong sleeping pill also. I used to take it for that reason, solely at night, now I take it during the day as well. Woke about 8am, took the morning dose of chlormethiazole, fast forward to about 6pm:P