I'm not going to argue for full-on bullet-proof pseudonyms, because I'm sure that would just be a matter of creating multiple accounts. The issue I have (and a wide variety of the "privacy conscious early adopters" using the system, I'm sure) is smaller: there's people I've been hanging out with online for the better part of a decade, and I know them by their pseudonyms. Google+ gives me a list of names I only barely recognise, instead of the familiar handles I've come to associate with these faces. Likewise, it would be nice if my user tile could show up in my parent's Circles with my given name, and my online friends' circles with my handle.
As another example, I have some friends of Chinese descent who have a "Chinese name" given to them by their parents, and an "English name" they use in non-Chinese-speaking contexts for the benefit of people who are inexperienced at pronouncing Chinese words. Their real-world relationships use very different names, but G+ forces them to pick only one.
A long-standing HN favourite post is patio11's "List of wrong assumptions programmers make about names", and one of the items on that list is "A person has exactly one name that they go by". This is exactly the assumption that Google+ makes, and it's just as wrong as ever. Circles is a great model for real human networks, but it doesn't go far enough: a single person can quite legitimately be known by different names in different social contexts.
As for myself, I've changed my Google Profile's "name" field to reflect my usual psuedonym, because more than half of my current G+ contacts know me that way. But I'll keep complaining about it, because I think it's an important part of human society that is being overlooked.