I've heard lots of people say that Mongo doesn't scale very effectively, but fortunately the nature of how Complice works as an app is that it's usually tracking small lists of things (eg "what am I doing today?") not massive ones (eg "what are literally all of the tasks I've thought of doing in the last 5 years?") and there hasn't been that much of a need for normalization, so it's worked well for me.
To be honest, I didn't think about it that much when I got into it. I hadn't worked much with databases before building this app, so I didn't have a lot to compare it to. I liked the ODM that is Mongoose because it let me mostly ignore how the database actually stores things and just treat my documents like saveable objects.
All in all I'd recommend my stack to anyone whose main innovation is in the UI or other interfaces. If you want to do something that's very technically impressive or efficient, you might be better off with something else.
WordPress plugins, all day long.
Many wantrepreneurs/micropreneurs/solopreneurs advocate starting with a WordPress product. They're right for many reasons. You don't need a lot of code or overhead. The product is distributed so you're not worrying about your server going down in the middle of the night. You can use WordPress's platform to sell your plugin. WordPress site owners are used to upsells.
But here's the secret sauce. WordPress site owners are constantly browsing the plugin directory and trying plugins because they're free and because it feels productive. They know they should be writing a blog post or managing their Google ads, but instead, they're clicking "install" on random things because the barrier to entry is so low. So as long as you can create a plugin that people might want to try, you've got traffic. Now all you've got to do is upsell them. :-)