Hans Reiser, author of the ReiserFS program, created benchmarking tests designed to be fairly representative of the file-size distribution of most users. "Reiser4 does quite well on all benchmarks," he said. "With Reiser4, we took five different technical gambles, and all of them worked.
Lindows, Suse, Darpa (The Defense Advanced Research Projects Agency) are major supporter of Namesys and reiserfs
I plan to use this fantastic file system (3 to 4 times faster than NTFS) as soon I have more report on its stability. Anyway it is already in use on a small partition (10Gb) on my Suse 9.2 box (but do not contains any critical data)