It’s 2010, Firefox is going 4.0 soon and it still has no way to tell why it’s sluggish.
Yes, it would be nice if the FF developers could make the browser so fast that it would never become sluggish in the first place. I just fear that this is simply not possible with the current design. Look at Chrome: Every tab runs in it’s own process. So what if one of them is slow? All the other still feel crisp.
If you care, support Bug 505104: Please add a tool to gauge Addon performance.
Firefox was fast in its early years… Firebird 0.6 and such. But now, It’s the same bloatware than everything else.
Nowadays, Chrome is the fast browser, but now it follows the same path as his predecessor: getting bloated with plugins, addons and functions.