For starters, I’ve always hated seeing a big long empty space in Safari for Mac when you have only one or two tabs open. The rest of the tab bar becomes an empty, wasted gutter of space.
Using that space for wider tabs, even with just one or two open, means that you can actually see the entire name of the page in each tab. This is one of the interface issues that drives me nuts about Chrome: every tab is the same tiny, useless width, so you never can make out much a page’s name.
Plus, on the iPad, using that wasted tab bar gutter space for wider tabs makes them not only easier to read (which is especially hand since Safari for iPad doesn’t display favicons on its tabs), but much easier targets to hit with your finger. Space optimization + easy tapping = a big win in my book.
Please, Safari guys. Think of the children, and their children’s children. Keep them tabs nice ‘n wide.
Update: Gruber updated his post in response with a nice idea:
A clever compromise that perhaps would make us all happy: If there’s room, grow tabs to be wide enough to contain the page title, but no wider.