I read it but I don't write there. If anything tumblr is the opposite approach - hackers would have gone to geocities, or wordpress, or at the least livejournal, all of which offered more power and control over your site. Tumblr took blogging at cut it down to its minimalist essence. Everything you can do there - and a lot more besides - you can do on any other blog host. But tumblr is very user-friendly and distraction-free; posting becomes as simple as writing. It's a great example of a product that does exactly as much as it needs to and no more, that solves one case perfectly rather than 80% of five different cases.
I use it a lot, but to read other people's blogs and discover interesting content.
I read it a lot, but I contribute zero. There is a lot of fun content like silly GIFs, but also amazing and creative music mashups, etc. I like Tumblr.