So the Google+ iOS app got released, I think it's pretty nice. They did a good job overall with the mobile site but it's just not quite as good as a native app.
The main "home" screen has 5 icons at the moment, big enough targets, gets you to the place you want. This is nearly identical to the Facebook app when navigating between functions; I am not a big fan of this; one place where I think a tab controller would be better suited; faster to use too.
The rest of the functions like photos and circles are pretty standard and work well. The Huddle feature is a good idea, data based group messaging, would save sending out lots of SMS messages, but it didn't work very quickly when I tried it and there seems to be no way to view these on the website. The Stream view has probably the most different from other apps. I will let John Gruber explain better than I would:
this Google+ app uses left-right swiping to change views in your “Stream”. I see three: Incoming, Circles, and Nearby. The idiomatic iOS design for this would be a tab controller at the bottom with three tabs, one for each view.
I do agree that it's not standard but I don't think it's a bad choice, seems quite quick and a good alternative, especially for only 3 separate views; if there were more then I dont think it would be as good. What I don't like about this setup is you can only swipe, there is no tapping the header of the left/right views; it just tells you to swipe. It's one of those things that should be perfect alternative that users can find out. I think Loren Brichter actually explained this very well in this interview from 2009 about Tweetie 2:
Now, I think you can split gestures into two categories. One is of the pull-down-to-refresh kind. These are gestures that are discoverable and explanatory. The other kind of gestures are like tapping-the-status-bar-to-scroll-to-the-top, or swipe-to-delete (or swipe-to-reply in Tweetie). These gestures you won’t discover on your own except by accident. These are not discoverable, and they are not explanatory.
This second class of gestures can exist (in my opinion) because they are not the only way to accomplish a goal. In the case of tapping the status bar, users already know how to scroll to the top manually. It’s slower, but it’s possible. In the case of swipe to delete, users already know they can tap on a message and then tap the trash button. So knowing the gesture isn’t necessary.
So when you’re inventing new gestures, it’s important to think about whether the gesture is required to use the app. If it’s the only way to accomplish a goal, you better be sure it’s discoverable and explanatory without needing to read a manual. If it’s the other kind of gesture, go nuts!
I would class tapping the header left/right text as the second type; you would probably only discover it by accident, but it would be a perfectly acceptable way to navigate. What I don't like at the moment is the big popup that appears telling you to scroll instead; it's an iOS app, we probably would swipe automatically anyway (plus I have a recollection that it gave you a message at on the first launch that you should swipe anyway).
I can see no reason to use the web app over this native one, it's a good start.