Yes, Modify is one of my most used and favorites! Love how we have the ability to mass update anything and can filter by tons of things to get exactly what we need updated without having to create a separate report in Salesforce and then export to do the update.
I completely agree on all your points! Modify is definitely one of my favorites for existing data - it is such a powerful tool. I even wrote about it on my first post Welcome to the Validity Community DemandTools Forum! because I love it so much! 🙂