Received an invite ages ago and never used it. In the view of many, including myself, Google+ is not seeking to become a Facebook clone per se, but rather as a way of encouraging people to establish real name profiles to better track them and their "friends" for the benefit of advertisers.
I have several separate Google related accounts all with no profiles - as long as I don't create any, the accounts will remain separate.
Been some horror stories of people who've created a Google+ profile and found their other Google accounts, such as Youtube, linked to it; issues with getting locked out of all their accounts for a Google+ violation, such as incorrect profile information - supposedly, total account lock out doesn't happen anymore, but some say it does in some instances ... not worth the risk of losing access to email, docs, etc over that.
Another aspect to consider is that once one creates a Google+ account and adds friends, there is no guarantee those relationships / data won't be exposed to those outside of the various circles one sets up. It's likely Google+ has better safeguards than Facebook, but, I for one, wouldn't trust it.
Sure, Google+ may be fine to use for professional networking, such as people do with LinkedIn, but for personal stuff, it seems no better than Facebook unless one assumes from the get-go that everything one posts is public and that circles, much like friend lists, are feel-good measures that offer little to no real privacy.
Also, many have the misconception that putting fake info in their user profile automatically protects them ... not so, as many Facebook users have found out. Contrary to popular belief, one's identity alone isn't the most valuable thing, but also one's relationships / interactions with others. A fake profile is only really effective when linked to other fake profiles that never mention anything factual - that rarely happens in the real world, in which they often link to real profiles and/or they and/or friends, which can include friends of friends, post factual information, such as where they live, schools, local events, clubs, etc. Point is, even with a fake profile, it's relatively easy to establish one's identity based on those linked to them - investigators track down people, with seemingly no identity and address, through relationships / activity all the time
Rambling on ... anyways, I've chosen to steer clear of Google+, and likewise with Facebook, etc.
Ron