A significant advantage of Seeker is that it is an interactive scanner, and we have found it to be much more effective in reducing the amount of false positives than dynamic scanners such as AppScan, Micro Focus Fortify, etc. Furthermore, with Seeker, we are finding more and more valid (i.e. "true") positives over time compared with the dynamic scanners.
One area that Seeker can improve is to make it more customizable. All security scanning tools have a defined set of rules that are based on certain criteria which they will use to detect issues. However, the criteria that you set initially is not something that all applications are going to need.