It's popular this medicine here, and despite of uselessness for a hypnotic rather than Flunitrazepam, widely prescribed. It's very effective for sedation and as an antidote from CNS stimulants induced symptoms.
I've had my fair share of nimetazepam (vacationing in Asia). The easiest relationship I can give you is it's in the same class as temazepam and nitrazepam. Especially the latter, not coincidentally. It's like a slightly stronger more fast-acting version of it. As people have said before, it is up there with the most potent benzodiazepine hypnotics. I'm sorry I can't be more specific, but my BZP receptors are dulled through constant bombardment.