I’m impressed with how much better than Firefox 3 the Firefox 4 betas look (especially on Vista/7 Aero).  However, when compared to Opera, Firefox’s UI (user interface) still has a major flaw.

When the Firefox window is maximized, those fancy tabs they finally placed at the top aren’t pushed all the way to the top like they are in Chrome. Instead, there’s a strip of useless, wasted screen real estate that doesn’t work well or look good.

Click a cropped screenshot for an un-cropped version.

Firefox 4 Beta 3:

Google Chrome:

Thankfully, since Firefox is so customizable, users can change this a bit and make Firefox’s UI a little better by editing their userChrome.css file as detailed here and here.  However, the hacks I’ve seen all still leave some ugly quirks behind.

If the Firefox UI devs don’t improve this before they make a formal release, I hope some crafty theme developers make some slick versions that look even better than the userChrome.css hacks.