I find the posts and discussion in G+ communities (in general, I am no referring any specfic community) to be in general to be terrible in quality.

For programming related communities, there are too many newbies who don't bother googling asking the same stupid question over and over. For some others, many are reposting the same thing that made it to the front page of HN or Reddit, to earn 'creds' I guess. There are a few obscure ones that post high quality content that I wouldn't discover otherwise, they usually lack lively discussions.