Hi! I am a new grower, but I have ONLY used ILGM (I Love Growing Marijuana, ilgm.com, or type the full thing out). I don't know if they're new or what. They seem to have the might of Dutch marketing and design behind them. That said, I am a newbie, but they have been good to me. When I was starting out and making a ton of mistakes, they gave me a lot of free seeds as per their germination guarantee. It was likely my fault whenever I had a bad grow or dead seed. Now that I am a little bit better (6 months in or so), I am having great success.
Here's a photo of my current grow (you do not want to see my first three, failures, or the ones that did not survive to become plants, however, what you see here is #4-8. As you can see, they are healthy and rather large for autoflowers maybe. I did do some LST, poorly, and broke the main stem almost in half on the biggest one (gelato, lower left), yet it healed and did not even complain. I have a new 2x4 tent now, and a bigger light on the way. This 2.3'x2.3' tent obviously is not fitting my needs (purchased to grow one plant at a time, but who has time for that?).
Bottom-left: Gelato; Bottom right: Banana Kush; Top-left: AK-47; Top-right: Girl Scout Cookies Extreme. There is also a blue dream in a 1g or less than 1g pot in the middle. It was originally meant to replace the Gelato, but the Gelato took longer than I expected (I did not understand "8 weeks" meant 8 weeks of flowering... they each spend about 4 weeks in veg, too)
I have heard people say bad things about ILGM, or about breeders who also sell seeds, but I haven't had any problems. The only problem I've had is the support staff not holding my hand as much as I'd like, but I don't know many/any companies that will really do that. They probably do it more than most do or can.
Prices are kind of high, in my opinion, but if you get it when they are 20 seeds for the price of 10, they come out to about $5 per seed maybe, which is okay, but yeah, a person might want to buy in smaller quantity and spend their money at Mephisto or something.
That said, I am ordering 20 Gorilla Glue autoflower seeds today for $140. That ends up about $7 each, which to me is kind of a premium price. Maybe I should be spending elsewhere, but they're been easy and trustworthy, and the plants are working well when I don't suck.