I use gmail, search and - for sharing specs and other docs - GoogleDocs extensively. Google products' formatting works better on Chrome than FF.
Wheensy little GoogleDocs bugs appear on FF.
On the other hand, FF has got this rich set of add-ons - and they're adding-on to their add-ons every week. How can you program without fireBug? And fireFTP is so simple to use. And ANT allows you to capture all those clips of Brea Barrett. And so on for many of the add-ons.
And FF's History has that magic button "Forget About This Site" so no-one else needs know you looked at Ms Barrett on tube8.com.
Also, as a Moodle FF (Frequent Flyer), Moodle's built-in HTML editor is badly screwed up by Chrome, works brilliantly with FF (and IE). I guess that editor's cousins are also screwed up on Chrome.
You still have to check your pages on IE. No matter what developers use in their ivory towers, the majority of your users still use IE. Fact.