Yes, the UI is still skinnable, and the default skin is rather... psychedelic.
There's something to be said about the adblocker being a filtering proxy, it can really get anything before it hits the browser.
Do you know how it compares to Privoxy nowadays? Way back then it was the open source but harder to configure alternative, that didn't quite work as well as Proxomitron. But maybe Privoxy continued development and got better, I don't know what direction that project took.
Oh and I personally always really liked the default skin :D
Nope - its green, and hasn't been updated since June... of 2003. I have no idea how it is able to be effective against the modern web, considering in 2003 the biggest issue was annoying pop-up Flash ads which no longer exist. Maybe there are updated plugins or something.
...which brings me to another great point this illustrates: if you want to customise your experience, if you want to be able to control how you see the Web, then you need to make an effort, and the amount you exert is essentially proportional to how much you can change.
Yet the majority of users have shown that they are willing to take whatever Google throws at them with little opposition. I find that a little sad and ironic in this era of "everyone can code" propaganda (I've seen even Google advertises something like that on its homepage); or perhaps the latter is just an attempt to increase the population of intelligent yet docile and obedient corporate drones... I know developers --- web developers --- who really hated the changes yet made no effort to fix it themselves, despite almost certainly having the skills to.