A combination of ultra cheap servers ($5/mo), high performance SSD disks, a great API for managing droplets (what they called their machines) and some super slick marketing meant that Digital Ocean has quickly gone from the new kid on the block to one of the biggest hosting companies in the world.
The droplets are awesome and their control panel is incredible for managing them. Low powered machines for $5/mo. is a great way to spin up a new machine for a few weeks to experiment with something new. The 2GB droplet, which is more suitable for production use, is $20/mo.