Indeed I'd say it's great for putting together an MVP (mainly because you can do it really quickly). As for the scalability I don't think you'll hit some limit after 100 users but of course it depends on your app too.
I'm a freelance web designer that is capable of coding my own designs in clean HTML5/CSS3(+LESS). I also have 5+ years of experience of using WordPress and more recently I've used Kirby as well. I've designed a plenty of responsive sites and my primary framework of choice is Bootstrap.
Lauri Liimatta. Finnish web designer living in The Netherlands. Looking for web design projects (Responsive/adaptive design projects are especially welcome). I'm also expert at XHTML/CSS/WordPress.