I've bought twice from Marijuana-Seeds.NL. Their stealth is *very* stealth. I had to look twice to find the seeds in the second shipment. They respond to emails promptly. Had a mixup on payment with the second order (when their credit card processing was down and wire transfer instructions contained an error. They worked with me to get it fixed up, and ate the wire transfer fee.).
The only potential downside I've heard is that they don't publish the breeder of their seeds. But, mine have grown well.
Someone said weed-seeds.net is a sister company and that the same strains are shown there along with breeder names. Don't know if that's true.
Maybe another downside is that they don't provide the tracking number. The package has a tracking number which can be looked up on the Royal Mail web site. But, m-s.NL doesn't give it to you. That may be part of their stealth. If it doesn't arrive, they can look it up. But, until them, only they know which piece of mail is theirs.
I always did the guaranteed stealth option. I figure they have more skin in the game and will take more care. But, I've read that it's better to do untracked, no stealth. That customs is less likely to open an ordinary envelope than a packet containing merchandise and/or bears a tracking number (indicating there is an intrinsic value inside).
For new growers I think m-s.NL's "value packs" are a huge benefit. You get a lot of seeds to make mistakes with. I.e., a new grower will feel less stress about a $4 seed compared to a $12 high-end (breeder-specified) seed.