Nirvana seeds have really good germination rates on the whole, sure you get a few people that say they get a duff lot, but its a biological product, there is no way for sure that nirvana can guarantee so many and the fact they send more is a sign of good will.
Nirvana's germination ratio is so good, just because of the pure numbers they shift, the price of them is too hard for most newbie growers to ignore, so nirvana have pretty fast stock rotation compared against jack herer from sensi seeds, which is a much better strain but doesn't sell as many, so your chances of getting bad germination rates are higher with jack herer from sensi than they are from nirvana.
What you guys gotta consider though is how many seeds nirvana do put out that go without a hitch, and that number is high.
Having said that, nirvanas stuff is low end stuff, the plants are not as strong/vigorous, their white strains like snow white, white widow, white rhino and such like are hard to tell apart in the smoke, they have a few reasonable strains, their bubblicious turns out pretty good along with a few others, but you can never achieve "da bomb" with nirvana seeds, only mediocre compared to what you can achieve with some skill and some dank seeds.