We ran into what we believe to be this very problem at SimpleGeo and spent a long time figuring out what the cause of the JVM locking up for tens of minutes at a time were; we believe this bug (or general class of bugs) to be responsible. Upgrading to 10.10 has caused the majority of the symptoms to disappear.<p>My personal hunch is that there are probably startups and developers that dumped Cassandra due to "stability issues," which were in reality symptoms of this bug. There's obviously no way of confirming or denying this, so I'll reiterate that it's just a hunch.
librato has an amazing product and continues to have a great blog. I love how they dig into the root cause (linking to the typo in the patch that introduced the bug) and also have easy graphs to take in the impact.
This applies to any AMI, Ubuntu or not.<p>Ubuntu shouldn't be used for web servers to begin with. You should be using a distribution with a long and thorough stable release cycle with minimal packages, such as Debian.