Nirvanna is a great way to enter this hobby. Excellent price and you can score decent seeds. They push out a lot of F2's though, which can result in a nuber of different phenotypes in one pack of seeds. Some don't like this, though if you are looking for a mum it might give you more choice. If you are looking for a particular strain and want the best genetics then a little research will send you to the right breeder (but probably not at Nirvana's prices). My 2 cents, there's better breeders out there, but it's a great way to get growing on a limited budget. Joey Weed seeds has great genetics at a fair price too.
Hope this helps