Ask HN: Best hosting service?

Hi, I am looking to change hosts. I've used services such as Bluehost, HostGator and Network Solutions. I've been thinking about moving to Amazon EC2 or another service, as I plan on launching my site pretty soon. My question is, what would be my best option for hosting my site? Aspects I'm considering are security, speed, price, backend ui and stability.

To put things in context, my site functions similarly to Yahoo Answers and Quora, in that users create simple accounts, post a brief article and comment on other's posts.