As a guitar player, I'm at the --- played it in my college dorm room, learned all the Nirvana songs --- level. That being said, your "demos" on the home page are incredibly awesomely impressive. And..... way way way beyond where I will ever find the time to get to. And when I clicked the "Play with an example" link I literally LOL'd!!! I may have no idea who your target audience is, but from this example.... it's not…
I'm at a similar guitar-level as you, but I'm delighted by the site. The hardest thing about ascii-tabs for me is to understand the timing. This fills that missing link.
The site is beautiful, and I'll use it, and even try to add a couple of tabs. This needs to live on people! :)