I like it. It's elegant and original. It's still fairly simple in design, and I'm finding it easy to use so far.
I've been reading some complaints on Google+ today, and there seems to be three. First, people with large hi-res monitors don't like all the white space and don't like how it looks. Second, people think the adding of the cover photo makes the profiles look too much like Facebook's profiles. And three, people don't like the chat panel at the right hand side.
|Google Plus in Wide Screen View|
|Google Plus in Narrow Screen View|
The other complaint I've heard is that it's not very intuitive. I actually haven't had a problem with that. It all comes naturally on the new interface for me. Maybe it's just written for the way I think.
|Google Plus Profile|
I think the profile looks classier than it did, and more business like. While Facebook's Timeline does look nice, it feels like something that's good for personal things, not for a business. The Google+ profiles feel very professional, and though not as "fun", seems like a much better design for business.
As expected, and this was already part of Google+, Google Plus has a much better search ability than Facebook. That has always been my biggest complaint about Facebook.
The sidebar controls take up less vertical real estate, so I don't have to scroll as much as I did in the old interface and in the current Facebook. And the fact that the bar stays static makes using it much easier.
I haven't really found any that cause me a problem. I think the biggest weakness is that while the new design is definitely an improvement in my opinion, it didn't really fix any existing issues Google+ already had. It's just basically an interface face lift, not a bug fix or a solution to known issues. And the added features like Explore and new ways to find people don't seem to be too useful, at least to me.