I think is largely aimed at the people who are using Google Apps for their own domain. I certainly wouldn't want a corporate account tied to my Google+ identity, but my own domain and email address which I've been using for over a decade definitely fit the bill.
Yep, that's the boat I'm in. I've got google apps for my own domain, and maintain 2 personal accounts on there (one for friends, one for acquaintances), my work is also on google apps. That means that there are already 3 google accounts that I'm juggling (or struggling with) and I was loathe to add a 4th account just to use google plus.
But it has further use as well. You can have your own personal identity on your gmail address and your official corporate identity on apps. Mixing roles is never a good idea and g+ on apps makes it easier to avoid.
