While the Firefox (and Open Source in general) zealots can get carried away at times, that article is spreading some half-truths of its own:
Web pages that depend on ActiveX or were only tested in Internet Explorer will only render and work properly in Internet Explorer based browsers.
This implies that any web pages that weren't specifically tested with Firefox won't work with it... which is pure BS. Most web pages that avoid IE-specific extensions and make some attempt to adhere to accepted HTML coding standards will work just fine, whether they were explicitly tested with Firefox or not.
Firefox is not only inferior to IE performance wise,
The only performance issues I've noticed are A) initial load time is somewhat longer than IE; and B) Macromedia Flash. Comparing load times is somewhat unfair, given that much of IE's infrastructure is already loaded as part of the Windows OS before the user launches the browser. I agree that the Flash plugin performance can be a significant issue for anyone who relies heavily on Flash.
but as soon as it gets enough market share and malicious code writers give it some attention, it will be more dangerous than IE as well.
I find that implausible. While I fully expect Firefox-specific attacks to become much more numerous, how do you justify your contention that it will become "more dangerous" than IE? That sounds like little more than unsubstantiated FUD to me.