SiteGuru is one of the best deals I've bought on Appsumo so far. Clean interface, well structured and easy to use for me. It's fast as well which is quite important to me, I hate other tools where you have to wait with a spinning icon each time you click anything.

My favorite feature so far is the prioritized to-do list which is easy to understand and to work through. It helps me always to start with one of the most important things to fix for now and not to waste my time on less important aspects.