Germany: we qualified from the month we registered, but the first payment took almost four months, because the family benefits office asked for more documents twice. Both times it was birth certificates and proof that the children lived with us. My advice is to send everything they could possibly want in the first application, including translated birth certificates, even if the form doesn't ask for them. It saves a round trip.
We've been in the Netherlands for a few months now and I finally sat down to sort out child benefit. Some friends here told me we'd get it straight away, others said there's a waiting period, and one said newcomers usually get it only for part of the first year. The official page is clear on the general rules, but I'm not sure how they apply to us, because my husband's work contract started before the rest of the family arrived.
Did you qualify for child benefits as soon as you arrived? Did anything about your situation (a partner arriving later, a job starting before the move, kids joining later) change the outcome? And how long did it take from applying to the first payment?