I have to agree with this since Mozilla is an organization that defends users' rights on the web. Firefox is just as fast or faster than Chrome in certain testing so try it out without heavy addons (like firebug) and try it with a fresh profile.
In any case competition is good. I don't think we'd benefit from a purely trident or webkit or gecko world.
The problem is, it's pretty useless without Firebug compared to Chrome, at least for me -- much of my browser use is for web development.
(this may change with the built-in debug tools set for Firefox 10.0 -- let us hope)
I'm also a bit perturbed by the fact that Mozilla has always touted extensions as a key feature of Firefox... only to say you should disable them all if you want good performance.
A big part of the built-in tools isn't to replace Firebug. It's to provide APIs for Firebug (and other addons!) to be able to do what they do even better.
Addons don't in general hurt perf, but it is definitely possible for them to. Firebug, in particular, disables the JIT so it can debug it, making Javascript execution painfully slow, and thus the browser is slow too, since large parts are written in JS. Firebug isn't to blame though; we just haven't provided them with APIs to do better yet.
In any case competition is good. I don't think we'd benefit from a purely trident or webkit or gecko world.