I wanted to do a bit of a review of your mod and give you a full outside opinion. I've been here since 0.0.1 and I'm rather surprised to see how quickly this mod had developed. At first I kept my mouth shut and decided to let the mod grow a bit before I said anything about it since it has a TON of potential. Yet, it seems to be growing into a fine mod and I'd love to give you my thoughts. I don't know how many people have done this (nor do I care), any review is a good one, (That is, if they keep bias out of it and actually attempt to help instead of bicker.)
I understand that it is still a Work in Progress, but needless to say, It's on its way to being popular. As noted by you, it was inspired by MAtmos and it certainly feels that way. People love MAtmos, yet it proved to be rather difficult. Yes, it could be easily installed and sent up and running, but for those who use modpacks such as FTB and Technic find a bit of trouble in getting the two (the launcher and MAtmos) to merge and still use the trouble-shooting launchers that these two offer. This is what made MAtmos so difficult.
Yet your mod offers a lot of what MAtmos offers and the only thing someone needs to do is plop it in the mods folder.
Not only this, you stay interactive with your users and reply to their comments and problems immediately, quickly letting out new releases and keeping people very satisfied. This is wonderful and I encourage you to continue this. (Though, just a piece of advice, don't leave this mod alone for too long. You may end up loosing interest and stop working on it altogether, and I believe this mod is something people really need.)
On to the darker side of this post. This is all opinionated and you can easily turn a blind eye to it, that's up to you. I'm leaving my thoughts here in case you want them, though. If someone acquires too may terrific, non-troubleshooting reviews, it doesn't help them to see flaws or kinks in their work... (I'm a writer and I know this personally.) Though, as said, turn a blind eye to this if you feel.
MAtmos is a wonderful mod, it was the first of it's kind as well. A mod that adds ambiance and make Minecraft more beautiful and appealing with natural sounds and realistic measures. Though, it's hit a few bumps lately, people are still attempting to keep it going and are still working on it.
That being said.
I understand that this is still a Work in Progress and that MAtmos is your source of inspiration. And this mod is a blessing in the area of simplicity. Yet, at first glance (when someone downloads this mod and puts it in for the first time) people have a big wave of MAtmos. Yes, there are small differences, but all together, the two mods sound the same. This isn't much of a problem for the mod users, since they like whats in front of them and enjoy the simplicity of this mod. Though, in terms of MAtmos, if you can throw in something really unique before your mod becomes really popular, it'll make it "yours". Otherwise, you may get a lot of MAtmos copycat messages (because people are too idiotic and naive at times).
The area of "ambiance" can be shared by mod developers, but they should have something that they can call uniquely "theirs" in their mods. For MAtmos, they were the first major mod in the "ambiance" area, so they don't have anything "theirs" because nobody else has stepped foot in this area and attempted to claim a piece of it. They are unique because they were there first.
My advice is to see what you can throw in that is your own. Something that has never been seen in MAtmos. So you have something to hold before the people who call you a MAtmos copycat.
I hope this helps. Everyone needs a nice, long review at times... Surprisingly, this took an hour to write... I usually don't have a problem with words.