I just got into Google+ this week. I installed the Android app immediately. It's a worthwhile front end to Google+. It supports the Stream, Photos, Circles, your profile and Huddles.
There...that's the summary. Now for a little detail.
Google+ is a social network. It lets you put people into "Circles" based on whatever criteria you might imagine. You can then post your content and list the Circles you wish to see it. You also have the option of making your post "Public" so anyone can see it. You can post text, links, photos and videos.
Google search provides a way to search into Google+ and find what you want. People are working out new ways to find things in Google+ all the time and posting tips.
The app also has an "Instant Upload" function that will upload photos and videos to a private library on Google+ attached to your account. I've tried it and it works. My phone uploaded over 700 photos and several very large videos and they all remain private unless I choose to share each one...and then only the ones I shared are visible. At present, you get unlimited storage for photo and video uploads with the sole restriction that videos can't be longer than 15 minutes...at whatever resolution. If you're paying for your 3G data you obviously want to be doing that over wifi only.
A "Huddle" is a group IM chat function. You can invite people into a huddle and everyone can see each others contributions. I tried it. It works. We had a little trouble finding each other at first, but after we added each other's gmail addresses to our respective Contacts in Gmail, we were able to locate other in Google+ and start a Huddle. This was only a day or so after the service launched in a limited way, so hopefully they will have that problem sorted soon.
Not all the Google+ web-based functionality is supported the the Google+ app. You can't do video or audio "Hangouts". It doesn't work through the web browser, either. I tried. You also can't see or use "Sparks", which are your custom searches for items of interest.....presumably to spark ideas in your head based on what it finds.
Overall? I'd get this app. It's stable. The functionality it has works. The Instant Upload feature could be an excellent way to share your photos....or just back them up to the cloud into free storage as you go along.