The google+ iphone app is very well done. I have heard third hand that google spends a lot of time writing low level interaction code (re-writing swipe gestures to be 20% faster, etc...) solely for cocoa. I am not sure of the truth of that, but this app is much better put together than most and really shines as a new release. The other google iphone app also has some really unique and thoughtful features (the help immediately comes to mind).

I wouldn't be surprised if they came out with an ipad app soon and that it was at worst, decent.

Normally Android apps (the 'properly' written ones) use the same code base across tablets and phones. Most of the layout is done as xml, with different xml files loaded based on the size of the screen, resolution, etc.

That being said I checked out the Google+ app on my Xoom and it does not appear that they included proper tablet configurations yet.