If your blogger blog is connected to your Google+ account, then you can enable Google+ comments for you blog. By doing so, all discussions of your blog posts on Google+, as well as your website will be integrated into your site comments. This is officially available only for blogger.
A WordPress developer has recently made a WordPress plugin, which will allow you to use Google+ comments for WordPress. You can download the plugin from the developers website or from WordPress plugin directory. You can also see it in action in the developers blog.
The questions boils down to this – Should you use Google+ for WordPress? While the social integration with Google+ will be a huge plus for your website, the cons outweigh the pros. You should stick with your current commenting system, instead of migrating to Google+ commenting system.
Google+ comment’s biggest drawback is that it cannot be moderated. While all other commenting systems like disqus and even Facebook comments allow the web admin to moderate the comments, in Google+, you cannot simply do that in Google+ comments. If your website receives any negative criticism (which could also be baseless – as in case of the internet) in either Google plus or your blog itself, you cannot down vote or block such comments.
Among many other drawbacks, another con is that the web admin will not be able to view all the comments. Thats right – you cannot even look at all the things people have to say about your blog. In the help page, Google tells that blog authors will not be able to view comments which are not shared with the author – meaning, you cannot even read your contents comments (Now why would Google do that?)
There isn’t even a moderation page for your blog comments, which puts your blog comments out of control from the web admin (who would want that?).
[ However, there are some plus sides too. Google+ comments supports hashtags and tagging other profiles to it, apart from integrating everything on Google+ with your blog.It also loads up pretty fast. ]
Disqus, the most preferred commenting system, is the best alternate to the default WordPress comments. Facebook comments is also a good option, if you want the one billion Facebook users to interact on your website. IntenseDebate is also a worthy alternative.
If you are a casual blogger, who wants something that is quick, eye pleasing, and just works – then Google+ comments maybe for you, else – stay away from it.