The search-engine giant has introduced trending topics and cover pictures, as well as a more "dynamic" navigation menu.
The company said more than 170m people have "upgraded" to the social network so far.
But critics say the number of regular visitors is much lower.
In a blog post, Google's Vic Gundotra wrote: "It's still early days, and there's plenty left to do, but we're more excited than ever to build a seamless social experience, all across Google."
He said the new features included "full bleed" media - showing pictures and video in full-size and quality - and "conversation 'cards'", which would make it easier to have threaded conversations, similar to the format found in Google's email service, Gmail.Stand-out features
The service now displays a list of the most commonly discussed subjects, known as trending topics. This feature mirrors microblogging site Twitter, which first introduced trending-topic lists on its site in 2010.
Also borrowed - from Facebook - is the cover-photo feature - a large image displayed behind a user's profile picture.
Cover photos were introduced to Facebook profiles as part of its timeline redesign and rolled out to its users over the past few months.
David Philips, a social-media and PR lecturer, told the BBC he believed the revamp had made it easier for Google+ users to use the network's stand-out features.
"It opens up the architecture of Google Plus so you can use many more of the features more intuitively," he said.
"I think it's now becoming a serious small-business tool, and also a very interesting tool for families where they can have lots of information shared among members of the family."
He added that while Google+ might struggle to stand out among its bigger, more active rivals, the breadth of integrated services would soon begin to work in the network's favour.
"I think this is a development that helps it carve a niche because it allows people to use so many different tools at the same time," he said.Techno Nigeria