Tumblr's strength is its presentation and it's a great medium for showcasing your aesthetic style & experimental conten.
There are strong communities here and a "fringe" dwelling of artists, brands, deviants and opinions that can be sorted to your liking.
Both flickr and tumblr know what to do with photographs - I'm surprised yahoo didn't use their superior interfaces to separate its failing brand from a plethora of visually inferior platforms.
Tumblr works best in an advertising - marketing capacity but its real untapped potential lies in the possibilities of a collective narrative.
The best use of the platform is art. Daily Rothko as an example...