Soft Launch
I'm pretty sure everything is ready to go. But, much like development previews, I'm going to let the forum crew mess with it a little before I mention it on the front page of the site.
You'll notice it's a very(!) simple site. There are only a few pages in total, but there are some neat details on each. (This whole experience was a tremendous update to my web development skill set on basically all fronts.) The site targets modern browsers with JavaScript enabled.
Song Bundles: Most songs include more than one arrangement: a version with the vocals/melody included in the piano part and a second version with the original piano part intact. Both are included for one price.
Full Arrangements: Any song in the store that originally featured instruments beyond piano will have them. Percussion is delicious. Every time my music guy delivers a finished product, I can't wait to play it and hear the beat. That is what all the MIDI songs in all the videos and other sites are always missing.

Aggressive pricing: For two versions of a song, $2.99 feels really solid for boutique content. That these are all brand new arrangements written from scratch, it's sort of an experiment to see if the store will even break even, hehe. I wanted to push even harder to have everything be at your typical iTunes price points, but that wouldn't have left much headroom for things like sales. And the margins would have been so slim after payment processor fees and mechanical licensing, there would have been little incentive for third-parties to provide quality content after I open the platform up.
U.S. Only: Again, the store is unfortunately limited to the United States only for now. (Other limitations include: no song previews.

Coming Soon
There are a few non-launch features I'm still working on (order history, gift cards, scoreboard tie-in, etc.) I'll probably mention something in this topic whenever I add something.
You'll also notice there are only 15 songs. That felt like a nice number for launch. Though there is a considerable backlog and one of the store's features is periodic, automatic releasing of new songs. That will be set up to unveil a new song each week after the full launch.
Right now the content on the store is biased pretty heavily toward typical American pop fare. Certainly there are a few older tracks in the backlog that will be popping up soon, but this seemed like a safe way to get started. Once I get a feel for sales numbers and how much sense it makes to hand-craft content that might not be as popular, I'm excited to start exploring things that might be a little more niche. (Something already in the backlog: a 5-song bundle of piano arrangements of classic videogame music.) The licensing story gets a little trickier, but I have been surprised by how much is able to be used from games, anime, and the sort.
You already have $3
Users with a desktop Learning Pack key get a free $3 store credit automatically. Your Learning Pack "short code" can be used in the promotion box during checkout as a $3 gift card. (That will get you anywhere from 1 to 3 songs.) If you don't know your short code (or got the Learning Pack before there was such a thing) use the retrieval page to learn it.
As a special bonus to forum regulars: if you (already!) have more than 50 posts, respond in this topic before Sept-15 and I'll PM you a promo code for another $10. (That's post count from this moment. Don't go spamming the board.

Use with Synthesia 8.6
One unannounced feature in 8.6 is that metadata for all the launch songs has been pre-loaded (like the G Major songs). You'll find all the usual stuff: hand parts, titles, library grouping, finger hints, along with the new "named bookmarks" added in 8.6.
The official 8.6 release just went up, so go and download it!
Feedback, feedback, feedback...
As always, let me know your general impressions, confusions, suggestions, ideas, or if you spot anything out of the ordinary. There is a ton of new work here that no one has laid eyes on outside of myself. I'm positive there are still rough edges. I hope all of you will be patient and help me find some of them!

I'm also interested in passing along any feedback you have about the quality of the songs to my music guy. This project has been literal years in the making so it's very exciting to finally show others. Please let me know what you think!