On Facebook: I find that a large number of my friends, men and women, use it. The UI is pretty reasonable for the things it does.

On Twitter: All the ugly @ and # syntax to work around the lack of forethought by the developers really pisses me off. On the other hand, custom Twitter clients like TweetDeck do some pretty cool things.

I find both Twitter and Facebook to have real value for odd things. To pick a random example, a Houston local microbrewery does one limited edition beer every year. You buy it on the day it comes out, and after that you'll never find it again. They were regularly tweeting all day about which supermarkets still had some left. To pick another example: at many technical conferences I attend, people will tweet with a hashtag for the conference (e.g., #usenix). You can set a search on that, and then you'll see chatter about the conference while you're there. This works remarkably well, although nothing terribly deep went by.

Standing back a few paces: "Microblogging" is definitely with us to stay, but I figure Twitter and Facebook will at some point both collapse in their heaping lack of profitability. Hopefully by then, there will be some sort of IETF microblogging standard that would allow you to run your own server and interact with others in some vaguely standard way that, so far as most users is concerned, looks and feels just like the centralized web sites, despite being a widely distributed system under the hood.