I can't imagine life without RDS. I'm a solo developer responsible for a large web app. Before RDS I hosted MySQL on dedicated hardware from Softlayer. I had a dedicated box for the master, one for the slave, and another for storing backups. The DB was about 100GB which made backing up a total nightmare. Mysqldump was too slow, I ended up having to use xtrabackup from Percona. Anyhow it got to the point were I was spending over 50% of my time maintaining the database instead of doing productive things, like building new features for my app.

Then I switched to RDS. I instantly fell in love with snapshots. I love that you can backup your database while it is hot. Sometimes, before doing a scary migration or query I'll take a snapshot just in case. I love that.

Even more amazing is the ability to scale up/down while the database is live. When I was with Softlayer and I needed to migrate to new machines there was always downtime and I always had to pay for both the new machine and the old machine for a small duration of time. Thus migrating would cost a couple grand in lost revenue and servers expenses, not to mention my Friday and Saturday night.