I've also had the pingdom monitoring on a droplet for the last 2 months and the only downtime I've been alerted to was my fault. Maybe it's on your end?

I used the LAMP stack (in beta) with a low traffic site running PHP5 + MySQL5. Nothing too fancy.

I'm using a 1gb droplet, ubuntu 12.10 with a LEMP stack, PHP5 and MySQL 5 for a low traffic site (Xenforo-based forum) as well. Maybe the difference is nginx vs Apache?

edit: I also added an additional 1gb as swap space, which helped prevent my mysql instance from falling over with low memory at times.

Apache defaults to using prefork on Linux.

Prefork is pretty much Apache-speak for "please munch all my memory and then lock up if more than a handful of people turn up at once".

Nginx or Lighttpd + PHP-FPM behave almost as badly if you choose dynamic mode and don't pick the right values.

I have had 0 downtime so far (2 months), and I've been monitoring with Pingdom with 1 second granularity. Which data center are you in?

Mine is in New York. Pingdom is configured to 1 minute resolution and I had 54 minutes of downtime in the last 30 days. Maybe I need to take a snapshot and spin up another instance. Thanks for your reference point.

No problem. I've been quite happy with them so far. I was using BuyVM for my side projects, but was getting annoyed with dealing with constant downtime, and other issues. I was starting to consider Linode, but ended up going with DigitalOcean due to the price. I really hope they can keep up the reliability that I've been experiencing.