Simply put difference between a 'hobbyist' and professional language for me is the strength and depth of the packaging ecosystem.
So as soon as you need to do things like open and parse PDF, implement TLS/SSL, create a dashboard,... you will be in trouble pretty quick in scheme. Probably simple stuff like handling unicode would be shaky.
I did write a web app that served a couple of hundred people with information, chats and live updates at a conference a friend was hosting. It was written in guile and made heavy use of delimited continuations which is probably my favourite way of handling state on the web. The main logic was less than 2000 lines, so it was by no means a large project.
What about the unicode handling would be shaky? And why do you say handling unicode is simple?? :)