I'm glad that the Maverick Meerkat EC2 images(1) are working great. In the latest Lucid Lynx image (24.9.) as well as in the updates for the previous ones they introduced a nasty bug(2) causing a phantom load of 100% on one CPU. No fix in sight yet; this was really annoying. In my experiments so far, Maverick Meerkat works just great!
[1] http://uec-images.ubuntu.com/server/releases/
[2] https://bugs.launchpad.net/ubuntu-on-ec2/+bug/574910