[which] ie7 v firefox

Firefox seems to be leading early on in the download race, and it's been more of a hit with the critics. One explanation for this is that, since Firefox users tend to be more fanatical and technology savvy than those of IE, they'd be more likely to download the new browser on the day of its release. By contrast, most IE users will wait until the new version of the browser is sent over automatic updates, which is expected to occur in November. If you have an interest in either of these, this is an interesting article.