I am happiest with the overall compromises and performance of XFS for my data, used in combination with ext3 on the /boot and root partitions. The XFS partitions hold either /var or /home (or both), depending on what purpose the system is put to. In my setups, /home is irrelevant for server-only systems, /var is where Postfix, MySQL etc will do I/O.
I have tried most of the Linux file-systems in the many years I’ve run Linux. Ext2 is fine for small disk systems, but suffers from protracted bootup-delays if the file-system needs checking. I ran ext3 for a while, then migrated to ReiserFS during my SuSE period (6.5, 7.x) after which I went FC3/4 using XFS.
For more on file-system performance, check out James Thornton’s overview, and this comparison.