This should be the next great text-editor once it's open-sourced - I'm too young to bother with vim/emacs, and a bit too poor to buy Sublime Text, great though it is!
The fact that it's written in Clojure(script) makes me want to dive into the source, and find out how a modern desktop application is built using a Lisp.
What does this mean? The younger the better, there's quite a bit to learn about using both.
If you mean they're too "Old-school" as in there are a lot of keyboard commands to learn to use them effectively...give them a try, you might find after a while that ctrl-n really is easier than moving all the way over to the down arrow key when you're in the zone and building something.
A modern IDE written entirely in Clojure would be Clooj (which IS open-source).
On the other hand, it has Paredit mode, which is still "coming soon" for Light Table :)