Can you float the google+ share button? If that floats (you probably want it to float left), then all the floats should work. Also, the reddit share button should probably float left also when that’s done.
Looks good to me. The only thing I would do, and that’s just me. It’s 8px shorter than the other three share buttons. I’d move it up 4px so it’s centered vertically with everything. That’s just me though. Not a big deal.