While there is no official Google+ support fr Windows Phone yet, that does not mean that you cannot use Google+. There are several 3rd party options available in the Windows Phone Store. Have a look:
My favourite is named “Google Plus” by Apps for Windows Phone. While I haven’t tried all of the available options, this particular app has a polished user interface and has all the standard features you would fine in the Google+ app, including write, comment, +1, explore, search, upload images, check in, and save photos to your phone.
At first launch, you are required to sign in with your Google account details:
You are able to access all your Circles, or individual ones:
Tap the Menu icon and you get this friendly sidebar interface:
The “Me” page:
And there is a range of options available in the menu:
Google Plus looks to me like a launcher wrapped up in the elegant Modern user interface. It is well designed and gets the job done.