Thank Heavens someone covered the issues surrounding Reiser4 in this article, as we all know Reiser4 isn’t in production in any particular capacity, it’s not being included in any major distributions and Hans Reiser is currently in custody awaiting trial. The previous link points to Wikipedia, where you can read about the situation and make sure to read the interviews and watch the video’s of Han’s discussion of Reiser4 and Namesys recorded well before the current situation.
Novell decided a while ago (before Hans’s current troubles) to make Ext3 the default file system for SLE 10 SP1 and beyond, but as the two file systems have been leap-frogging each other in features for a number of years, ReiserFS could very well be the default if circumstances warrant it in the future.
In the meantime, give the above-men tioned Linux Kernel Mailing List-inspired article a read, the summary at the top basically tells you all you really need to know unless you want the entire set of input and responses that led to the summary, it’s included as reference.
Hope this helps folks understand better about Reiser4 and it’s not being included in the distributions.