The point is that when you click on a tab, stuff _below_ it changes. A tab is not an element "click me and all around the screen stuff changes". A tab is an element that tells you "if you switch to a different tab, stuff below me changes".

Now look what happens when you currently click on a different tab in Firefox, Safari or IE: stuff changes below it (the page) and above it (the URL in the address bar). This is illogical! It dillutes the meaning of a tab. And it makes it difficult for normal computer users to understand the concept of a tab. Placing it the way Google does does now fix this.

This is first and foremost an issue of correctness and preserving the concept of a UI element, not a question of taste.