A couple days ago, my Google+ invite finally started working again, so I immediately signed up for the service.
If you want to know what it looks like and what functions/features it has in depth, I would suggest that you read somewhere else, because these are just my initial thoughts about it.
There are only two big issues that I have right now. The first is that not all my contacts on Facebook are using Google+ yet, but that'll probably happen in time once Google+ becomes available to the public, so that's not a really huge issue. The second is that when I decided to enable video chatting on Google+, I had to download a new Google Talk browser plugin and install that. This also overwrote the existing installed plugin; the unfortunate side effect has been that although my webcam and mic capture my video and audio fine, my speakers have suddenly started rendering sounds from the conversation as if both myself and the other person had inhaled helium. I haven't tried this with headphones yet, so I can't say for sure if this is truly a problem with the plugin, and I haven't tried this on other Linux distributions yet (aside from Linux Mint 9 LTS "Isadora"), so again I can't say if this is truly a problem with the plugin, but in any case, it's a problem, and it's also present in GChat.
Otherwise, I have high hopes for Google+, and I hope to use it just as much as Facebook once it becomes available to the public.