There seem to be a lot of G+ plugins out there, but this is the only one that seems to be updated. That's a good thing.
However, the others say (don't know for sure, since they don't work on latest WP) that you can put the G+ badge above or below the post, etc. Apparently, this one only posts at the bottom of the page (floating, but at the bottom, where it is easily ignored). I would much prefer the ability to put it at the top.
Still, not a deal breaker, so it still gets 4 stars, but if I find one that does that without issue, I'll switch.