Love it. There are elements of this that remind me of Plan 9's Acme and the Plan 9 shell. Contrary to many people's opinion, using the mouse in concert with the terminal is a really powerful paradigm.
I was thinking the same thing. But while I've always loved some things about Plan 9 (its security model and it going all-in on the everything-is-a-file model), I never was able to adjust to acme.
Acme is the part that I use even under OS X. The regexes are cool (they are recursive), it is easy to process a selection through a shell command, and the compiler integration is both simple but really useful.
I think what I like so much is that it is a rare example of an expert ui, designed for when you are really proficient rather than for learning or discoverability.
