If you'r a fast typer and don't pay much attention to spelling or English isn't your first language? No biggie, you can get a spell checker add-on for Firefox.
Not only that you can share files — like documents, images, and PDFs — without having to email them as attachments. You can share the whole folder containing the documents.
If you activated the new Inbox Tabs then after a while you find yourself not liking them that much and would like you old priority inbox back, this is what you need to do.
Google Chrome has a handy function where you can just paste an url or search term and you will go straight to the page or get the Google search results.
Many times I find myself with a large number of opened tabs in Firefox browsers and thankfully you don't need to close the program in order to close all the tabs except the one I want to keep.
Really great and free service where you can chat using a bunch of services like Skype or Google Talk within your web browser, meaning you don't need to install anything on your computer.