I like Firefox. If its not broken, don't fix it.
I thought MS-DOS worked great! Why did we need anything else?
In the spirit of innovation and development, new ideas and features are always a good thing. Google is trying to fix some of the pitfalls that plague other browsers. Specifically, this browser has a rewritten Javascript engine which is confirmed to be
much faster, as well as a new process management model: Every tab has a separate process. The big deal about that is that if one tab crashes or hangs, it doesn't make the whole browser crash. Even on my new laptop, with 4GB of RAM, Dual core yadda yadda, if I go to the file manager for my website (run by Javascript) and select one of the directories with LotR cards/images (~3500 files), the whole browser hangs. This happens for both FF (2 or 3) and IE. Maybe in about 5-10 minutes it will start responding, but it's as slow as ****! My only recourse is to kill firefox.exe and lose all other tabs I have open. I've had to learn that the hard way.

And there have been times where FF has crashed on me for no discernible reason (probably some poorly designed website).
Another one of the features that Google is advertising is better memory management. FF3 is better than FF2, but they both use a lot of memory if you have a lot of tabs open. Say, 15. When you close them, it doesn't always release that memory. Chrome fixes that with its multiple-process model. When you close a tab, it releases the memory back to the OS.
In any case, Google has made the browser open source and given other companies and users the opportunity to learn from its improvements and put them in its own software. Some of these features may make it downstream to FF.
