No more or less than normal benzos is my best guess.
Note: Zolpidem can cause hallucinations at the near sub-blackout threshold that present as nothing short of bizarre delerium. It has happened to me and it was not only unexpected but were scary and blackout did occur.
There is no easily attainable "sweet spot".
My advice is to not dose heavily on them or, if you must be a warrior psychonaught then take my advice and borrow a friend/sitter.
As ever, take care and remember that less is more.