Internet Explorer is generally regarded as a reason we can't have nice things, so this is a huge step in the right direction for Windows users.
Fun anecdote - last week someone at Steam wrote one of the sale pages using entirely -webkit- prefixes. It showed up blank in Forefox, but rendered fine in Spartan and Chrome.
From a business sense, it works because if it works in Chrome and fails in Spartan, it's our fault. From a user experience sense, it also works because they deserve to have their sites work.
However, I constantly see people complaining online about IE. What can I do.