Career: Ninja or super multi-functional

In my self-employed "summer vacation" without a standard day job, I find myself working on things that I'm interested, a luxury you obviously don't get whilst working for The Man. Some of it is naturally for the now five-years-old CoasterBuzz, which is an embarrassment of a site for me to look at (despite its continued financial success). What I've been into is AJAX stuff, building controls of all things. Every control I build is easier than the previous, and I find myself feeling ninja-like around the AJAX framework. I really enjoy working on this stuff.

I'm wondering though, as I now think about going back to work full time, if being a ninja is valuable these days. It's hard to be a ninja at all things (or at least, it is for me), but I find that really getting deep into something is rewarding personally. But is it valuable to employers? While I'm all giddy about ASP.NET AJAX, I've done little more than give MVC a casual glance.

There is always something new to learn, and I find that few developers, unfortunately, endeavor to keep up on it (which exlpains why there are so many COBOL-only devs out there). If you had the time on your hands the way I do, what would you be doing? Girls love guys with computer hacking skills (gosh!).