Except it's actually worse than typical frontends. It's maybe cleaner looking, but it doesn't allow you to test all font types at the same time.
http://www.network-science.de/ascii/ This one exists since 1996 and allows all fonts to be rendered. Option is very far on to top of font selection drop—down.
Edit: that to this
This!
I did my own take on this that addresses both of your concerns:
1. Update as you type
2. Show all fonts