It is a great place, its friendly, you can discover new artists and you can get excellent advice, both directly and indirectly, on just about anything to do with music, not just ambient, although ambient is the reason I came here. There are musicians here who I have the deepest respect for, although they may not know it.
I look upon Hypnos as a "serious" forum, that is "serious" in a good way, the advice you get will help to steer you in the right direction.
Pretty much this. I originally joined to spread the word about my music but there are a lot of knowledgeable people here, whether it be the veterans of the genres or the fans that post here regularly, and it has helped me to realize that there's plenty of great new ambient music out there. I love this forum.