Some thoughts on this thing:
It's fun to play in a new space without being burdened by all my old stuff.
The real time feed updates are exciting when they happen but only because there aren't that many feed updates yet so they aren't overwhelming.
If I had more time I would invite a lot of people because I'd get credit for being the one who let them in.
The "plus" brand is pretty bad. It doesn't feel like a space. It isn't something I would think to type into the URL bar. It also has a weird relationship to +1 which should just be called Like.
There is too much derivative/imported data. When I see faces it isn't clear if they're people who are actually on this or people who haven't signed up who I'm going to accidentally bother. That makes me not have that much confidence in the system. As an example of this, Google suggested another version of myself to go in my circles. I think it was from some other email address I have but now there's a ghost with my name floating around making me uncomfortable.
Managing circles is too much work. There should at least be a base level of relationship below the decisions about circles. The privacy around other people knowing who's in circles is unclear. It seems like people can tell who's in any of my circles but not which ones they're in, although maybe I just haven't found the interface for that yet.
They need to make search real time. People who just signed up who are in my circles aren't showing up.
Sparks has nothing to do with the rest of the product and should be killed. There are too many new concepts being introduced at the same time.
Photos should be more central. They should give up on pushing Picasa and start from scratch.