Did anybody ever MAKE those claims?
I've never heard anybody say that Firefox runs on slower systems or runs faster. With all the extra goodies you get, of course it's going to be slower. There's an extension for Firefox to preload links into memory. It's an assholish thing to do on slower sites, but it speeds up browsing tons, if that's what you're into.
Next, the marketshare. Mozilla themselves admitted that they made a mistake. Who cares?
In terms of security, most of the vulnerabilities for Firefox were really lame, and for the most part they were patched very quickly. Opera may have less vulnerabilities, but they aren't so fast at patching them. Obviously extensions can have vulnerabilities, he's pointing out the obvious. And who said that installing Firefox will clean up Spyware? That's a strawman argument.
The "memory leak" section is the dumbest one I've heard. They cache pages for each tab that you have open (they can't really not catch pages) at, so naturally, if there are a lot of tabs open, it's going to use a lot of memory. Duh. And OMG, Firefox has bugs? No shit. Who said that Firefox is the first browser with integrated search or popup blocking or tabbed browsing? Another strawman; nobody ever made that claim. (I notice on the Firefox page they used the word "innovative" -- that was a dumb word choice. I think that they pulled a Microsoft there, using the wrong word.)
I also wonder where they get the statistic of 10-15% of webpages not working. In my travels, I've seen 0 that don't work. I don't know about you, but while developing pages I've found the Firefox generally works better. That's an opinion, though.
The vast majority of the arguments they make are strawman arguments. They put words in somebody else's mouth and then shoot them down. It's an invalid argument method, and that page is almost completely full of crap.
