What's the best NAS for home usage with Macs? Please share your experiences and reviews about NAS (Network-Attached Storage) below. In particular, rate their compatibility with Macs, OS X, iTunes, Time Machine, AppleTV, and other Apple-specific tools. The goal is for future users to be able to easily find the best Mac-compatible NAS appliance.

Rules:


Use a single answer for each NAS (no duplicates, please).
Vote (up or down) on any NAS you have experience with.


Also welcome: useful reference links, such as this one from xlr8yourmac.com.
Synology DiskStation
The Synology DSM software has built-in support for Macs including Apple Fileshare Protocol (afp) and Time Machine support. It has an iTunes server in addition to a regular DLNA Media server. As it is Linux based it is easy to configure the NAS to do rsync backups (ssh login).
It has a great web-based desktop-style interface that is very easy to understand and use. The DSM software is constantly being updated and improved.
They have solutions from 2-disk on up to 15-disk.  You can find the 4-disk DS411j without drives for less than $400.