I've bought seeds from lots of different vendors and my experience has been that, generally speaking, the main concerns are price and selection. I've almost never bought seeds that didn't grow. I did once buy a packet of 4 o'clock seeds from Harris that were all duds, but they refunded the purchase price with no problem. (Wish I could say the same for Summerhill...but that was several years ago.) Unless it's something really exotic and you're concerned about getting the right plant, seeds are pretty safe from just about any vendor. With the possible exception of some of the folk selling seeds on ebay. I've gotten some strange and exotic things from ebay.