A really well crafted Google+ experience for the iPad would make it stand out.

I can't speak to Facebook's iPad interface as I don't use it, but G+ on the iPad is pretty awesome in my opinion, just through safari.

It's not a native app (through the app store), but it's a really nice just-for-ipad interface that suits me just fine.

Author: have you not tried this and are therefore unaware, or do you simply disagree with my opinion that the site they serve to iPad users is easily good enough?