After a couple days of playing with it, I haven't quite identified what it is for, or at least how I'm going to use it differently from twitter or facebook, but so far I am generally impressed - it's easy, intuitive, and fast. It also allows you a level of selective privacy that - while possible to achieve - is very clunky on Facebook. It only took me 10 minutes on the web interface and another 10 minutes after downloading the Android app to figure out how it all worked. And Google+ is already far better integrated into the mobile user experience than Facebook is (though this is to be expected for a phone that runs Android).
Yes. I haven't used Google+ much, but: 1 - The user experience is manifestly superior to Facebook's still. Interaction with the UI is more fluid and natural. Again, this may be due to the fact that it can be superior because the user base is small. No idea. 2 - The circles are great. My Facebook requests I mentally put into two categories. One category are people who I recognize immediately. I know them. Another category are people I'm vaguer on in terms of details (often they're readers who don't comment much, etc.). With circles I waste a lot less time being confused. If I don't know you well, I put you in the acquaintances circle. Period. 3 - The Google+ Android app is very good. Much better than what I have for Facebook. Then again, I haven't really utilized Google+'s features too much, I've just accepted people who make friend requests. Lots of the comments I see in my stream are to the effect of "hey, can Google+ do this?"