My "Narrow, Intense Interest" was/is computers, and I found I spent too much time fiddling with them (which I naturally did in Linux). I bought an old, used Mac to replace my PC a while ago, and now find that I simply get more work done on a Mac, because for the most part, it just works, and there isn't much you need to fiddle with. The amount of time I spend on a computer is decreasing, and the amount of productivity I accomplish on a computer has increased, which is a good thing for me.