I got an invitation to G+ on Friday July 8th, and signed up a couple of days later.
These are the reasons I’ve found so far:
- G+ has a slicker and more responsive interface
- Increased access control via Circles
- Simpler group communication via Hangouts
- Efficiently add interest feeds via Sparks
- No annoying games (farmville, ++)
- No annoying ads
Additionally, I think that it is great that Facebook gets a direct competitor. Of course, it is crucial that G+ gets traction, something that will most likely happen once G+ goes public and opens up its API.
Read more of pros and cons at Mashable.