I like that it can be used for both internal or external pentests, as well as penetration testing of cloud environments (AWS/Azure).
The UI is very easy to use even if you are not familiar with command line tools - just install an extension pack from their website which will add many more functions than they have listed at this time. It helps me run all my tests quicker by having them automated rather then doing everything manually myself. We've been able to find issues faster because we're running our own scans instead of relying solely upon what's provided through third party providers such as Qualys etc., also saves us money since there isn't any additional cost associated when using PTTs services versus other vendors who charge higher rates per scan performed.