Seedsman: mixed results from them. 2 really bad experiences, 3 really good experiences, and I learned the hard way that their in-house strains can be pretty shit.
Seedsherenow: higher prices, but the best service I've ever seen, super dank strains, fresh beans, unmatched quality guarantee. Money well spent.
New420Guy: good customer service, fast delivery, haven't grown those seeds out yet, so I'm unsure on the quality, but every order gets freebies. (Be warned, the guy that runs it is a super right wing conservative, as anti-immigrant as they come, if you're okay with that, cool, if not, now you know. I wasn't okay with my money being invested in that kind of thing so I use other seed banks now.)
ILGM: I believe they are shipping from outside the U.S. so seeds took a long time, first order never made it to me. They make me wait over a month, finally resent them, and I received the second package. Prices use to be a lot lower, but they've jacked them way up recently and they aren't really a bargain at all anymore. You're almost better buying them from better breeders. ZERO information concerning what genetics are actually being used to create the strains. If you sign up for the mailing list, no amount of effort or computer skills will get you off their email list.
Strainly: I've had a mixed experience, some because of the sellers, and some because of the interface. I'm the type of buyer that researches everything I buy, especially crosses. Strainly's interface doesn't really have a great system for listing parentage of strains, although, most of the sellers on Strainly right now seem pretty lousy at being responsive or having any customer service skills, so I'm not sure a better interface would help. I think @Strainly could put a dent in this problem by offering a popup or highlights window where they give customer service tips. I accidentally listed seeds I was actually hunting for and got slammed in the face with way to many scroll menus. Overall, I have a lot of hope for Strainly and even after some mediocre experiences, I've still purchased half a dozen strains from multiple sellers and visit frequently.
(Sidenote: Weedmaps and Leafly started out with the same menu/listing issues and both are bigger than ever, so I have great hope for Strainly.)