Most of the improvements and major changes in version 7 are under the hood, but at first use you will notice the difference. The scanner is much faster and seems more intelligent (there were noticeably less false positives than I remember in version 6) and it has much better support for Web 2.0 and AJAX powered web applications. That is of course a huge area now and very important for a tool like this that focuses on Web Security to support well (the modules have been re-written to support technologies such as such as JSON, XML and more). It also helps that it uses new unique verification techniques so you don’t have to wade through all the false positives by hand.
Note — This post applies to an older version of Acunetix