Has anyone used Hadoop?

Has anyone used Hadoop? Here's Red Hat's current method for Hadoop as I type this. We are looking into Hadoop.

From the first link, here's a brief description of Hadoop:
http://hadoop.apache.org/
- What Is Apache Hadoop?

The Apache™ Hadoop® project develops open-source software for reliable, scalable, distributed computing.

The Apache Hadoop software library is a framework that allows for the distributed processing of large data sets across clusters of computers using simple programming models. It is designed to scale up from single servers to thousands of machines, each offering local computation and storage. Rather than rely on hardware to deliver high-availability, the library itself is designed to detect and handle failures at the application layer, so delivering a highly-available service on top of a cluster of computers, each of which may be prone to failures.

Here are the current known users of Hadoop.