My personal opinion is that it could well be a flop. With the "like" button people are so familiar with this due to so much Facebook usage. The average Facebook user is logged in most of the time, so they know that by clicking on like they will be sharing these with their social circle. With +1? What does it do? You click it, then what? Who see's it?
You and I know that it will show in the SERPS if someone you know has previously +1'd something but does the average joe bloggs know this?
When it comes to the average user on the web I don't think they will have a clue about +1
As for placing a +1 button in the SERPS I am not sure on this. I mean, you search, get the results and then click on the link. You then going to view the page and then remember to go back and +1 it? I am more likely to click on my Evernote widget and bookmark it or if I want to share use my hootsuite hootlet and share it to FB or Twitter.
Really not convinced on +1 yet, but time will tell.