Now the cynic might say that the Google Plus brand team wanted to reduce confusion with their social network's name. The result: the 'new tab' icon in Chrome 17 looks like it's faulty.
It might sound like the most pedantic obsession over minutae, but stuff like this matters.
It matters not just for us user experience people who pore over every detail, but for 'regular users' who are forced to approach interface after interface: re-learning the basics over and over because of design decisions made without proper thought.
Here's the new icon:
Internet Explorer hasn't had a 'plus' icon for years, but it's part of the tab bar. In Firefox it's tab-shaped and features a 'plus' symbol. The new button in Chrome is a different shape, location and colour to the tabs - how would a first-time user know that this opens a new tab? Even if they work it out, it's an extra level of cognitive stress that should be totally unnecessary for the user.
If you're interested in reading more about how complete novices use software, this is a fascinating read, from Jennifer Morrow's blog:
I find Joe, a 60-year-old hospital cafeteria employee, in the food court looking suitably bored out of his mind. Joe agrees to do a user test, so I begin by asking my standard demographics questions about his experience with the internet. Joe tells me he’a never used a computer, and my eyes light up.