Congrats, Hex!
I tried yWriter briefly, but found the trouble was that I spent more time filling in all the bits and pieces rather than actually getting on with writing anything. Also, there didn't seem to be any sort of grammar/spell checker.
Is Scrivener the same? I heard it had some sort of timeline thing (does it?) which would be really handy for my WiP.
I haven't tried yWriter, as it's Windows software and I've been pretty much Mac-only since about 2005. Looking at the screenshots, Scrivener has a similar document list down the left-hand side (though it allows you to create nested folders if you want them), but in the default layout the main focus is on the actual text you are writing rather than the peripheral information about the document.
When I'm working, I hide the "Inspector" (the right hand panel that contains the synopsis panel, notes, etc) so that it looks kind of like this:
You can even run it completely full-screen if you prefer minimal distraction, but I find this pared-down layout to be a happy medium.
Scrivener for Mac uses the built-in OSX spellchecking tools - I don't know how Windows does it. I do know that if you want to spellcheck the entire manuscript, you have to select all the documents in the Binder (left panel), then click on the "Scrivenings" button. This gives you a sort of temporary single document that you can work on as a whole.
One thing Scrivener doesn't have is a timeline. I use
Aeon Timeline, which is designed to complement Scrivener's functionality, but it's OSX only.