There are two primary ways that drive-by downloads are done, either through a vulnerability in IE itself or an add-on, or because the user has the security setting set too low.
Beta 1 was really just plumbing. There was a little bit of user interface shown there, but it was pretty light. This release is much richer from an end-user perspective, as well as even on the security front. There is a lot more there.
RSS is probably the biggest area of innovation in IE 7. We've done work both on the end user to expose the average user to RSS in a really great way and we've done a lot of work on the platform to enable RSS for any application to take advantage of.