IMHO Google+'s principle problem is that it's multiple efforts all under the same name umbrella. This is confusing to users and seems to have been confusing to Google. It's a longer-than-twitter public broadcast messaging system/social network/photo sharing/single sign-on/half a dozen other things. There's some great ideas in there. Having a subscription style feed of people I want to follow, and their long-form post…
If I can subscribe to feeds, and set a preference for specific individuals on those feeds, I get a vastly superior information product. You can roughly approximate this via search in G+, but only roughly.
The lack of ability to follow people's topical posts (that is: show me +JohnDoe's post to SomeCommunity) was simply idiotic.
Reddit, subreddits, friends, RES dashboard, and RSS feeds give me much of what I was hoping for from G+. And a hell of a lot more utility.