Whoa. That's *huge*. I mean, that is the number-one feature I've been wanting from LJ since I first started here. It's not as good as I'd like (which would let me specify specific tags for specific custom flists), but it's a big step forward.
Of course, it implies that I should try to be more consistent about which tags *I* use, so that people can filter me appropriately: I suspect that rather different sets of folks are interested in the "programming" vs. the "sca" vs. the "politics" tags.
But I'm going to have to go through and give this some real thought. Frankly, there are a fair number of people I haven't been able to follow as regularly as I'd like, simply because of volume. But given the ability to follow a specific subset of their entries, it might be worth revisiting.