On my laptop, I love Google+ like Winston loves Big Brother at the end of 1984. But on my phone, I don’t love it very much at all. And I’m not alone.

Shortly before Google+’s native app for iPhone was released on Tuesday, Ancestry.com founder and “Google+ unofficial statistician” Paul Allen projected that Google+’s skyrocketing growth was beginning to slow down. From a high of 2 million users per day, new signups had dropped to approximately three quarters of a million. In a follow-up comment, Allen guessed that that day’s release of the new mobile app might have “a slight positive impact” on growth.

But just how many new mobile users would sign up? And what kind of experience would they have?

Many current and prospective users were disappointed right away: the new iOS app is iPhone-only, leaving iPod Touch and iPad owners out in the cold, unable to Huddle for warmth. WinPhone 7, Blackberry, and Nokia smartphone owners are likewise still limited to Google+’s mobile webapp.

Google+ Huddles, a kind of group text message, are mobile-app-only. So is the “Nearby” stream, a location-based timeline of public posts from nearby users. It might be the iPhone’s GPS-augmented location service that makes it, rather than the iPod Touch and iPad, at least some of which are Wi-Fi-only, tailored for G+’s mobile app.

By far the most common complaint among both iPhone and Android mobile app users is the inability to reshare other users’ posts. As I alluded to in yesterday’s longer Google+ story, the lack of this functionality, at least in the early days of the app, suggests that Google+ is competing less with text/news-driven social media networks like Twitter, and more with multimedia and location-based applications like Foursquare or Color, where “social” is defined somewhat more loosely.

While you’re on the go, Google wants your location, and it wants your photos. (Not all iPods or iPads have cameras, either.) It wants you to check for new messages. It doesn’t really care (yet) whether you share them.

There are two major differences between the Android and the iOS apps, one obvious and the other less so. The first is that Android phones allow you to auto-upload photos to G+. In fact, once you install, G+, the default is to auto-upload the pictures to Google (albeit to a totally non-public folder); you have to disable it if you don’t want your pictures going to Google at all.

I missed the second difference until my friend Andrew Simone called it to my attention. The iPhone app, unlike the Android app, doesn’t have a landscape view or keyboard mode — either using auto-rotate or as an option. So if you prefer to type on your iPhone with a wide keyboard, you’re out of luck when posting status updates or comments in G+.

Daring Fireball’s John Gruber complains about inconsistencies in the iOS app’s user interface:

The Google+ app feels like it was designed by people who don’t like the standard iPhone design idioms… It’s certainly not Android-like, but it’s not iOS-like either. For example, [it] 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. Google+ has a thin header at the top of the view, showing all three, with the current view in the middle, in a slightly larger font size. To switch from, say, Circles to Nearby, you swipe left. But you can keep swiping left, left, left to cycle around, like a carousel.

“It does not solve my fundamental problem with Google+,” Gruber writes, “which is that it feels like work to use.”

I’m going to hold off on final judgment here. It’s still very early in the life of Google+, and even earlier in the life of its cross-platform mobile apps. But I’ll just say that right now, its mobile and desktop pieces don’t really seem to fit together.

That may slow down its adoption. Given that G+ is still the most-downloaded free app in Apple’s App Store, and Google still hasn’t made a big advertising push, ramping up growth might not be the company’s biggest priority. But maintaining user enthusiasm for the platform ought to be.