Here's an impression from my first night of Google+:
This is very cool and slick interface but I can't help feeling that for a user from scratch it doesn't offer instant satisfaction.
You need to be a reasonable user of Gmail to get something to appear straight away, though you can connect Yahoo and Hotmail address books to get a larger list of people to invite.
I would like Google to make Sparks more prominent because it is something which you can do, after you edit your profile which Google+ asks you to do, before your circlets accept your invitations.
Sparks is just like customized sections in Google News and that's fine.
+1 from Google is integrated into the profile page and is very nice. It's like how I use starred items in Google Reader but for the whole web because of browser extensions. However I can't find an easy way to +1 and then share that from the feed.
Google+ on both iPhone and Android is there and works fine but is limited without many friends. I should start following people. Can't find Sparks in these apps yet unfortunately.
More as I figure it out, find me on Google+ if you want.