So what do ya think of the new Firefox 1.0 browser? When do we need to become concerned with developing our sites to also be compatible with alternative browsers such as Firefox and Opera?

CNET's New Year's resolution for Firefox: Grow article mentions the increased popularity is growing momentum. It also mentions interoperability problems will continue to dog users of this browser.

I just downloaded Firefox 1.0 to perform a quick comparison with IE 6.0 and Netscape 7.1. I am not impressed with performances of several sites I tested, including my own, while using Firefox. Menu bars and other site features often do not perform properly. And Firefox does not perform significantly faster, as claimed, than the big two browsers on my PC.

Since my traffic stats report the vast majority of visitors to my sites are currently using IE and Netscape, I am not going to worry about interoperability with these alternate browsers at this point.