I haven't investigated the ext2 issue with Linux all that closely, since we don't run any Linux IMAP servers in production.
We do run a number of Linux SMTP (Sendmail) machines and have been pretty happy. We use ext3 on them. I think the documentation will probably mutate more and more to just "don't use ext2 and Cyrus together" and encouraging people to use one of the modern Linux filesystems. We use ext3 mostly because it was easy and its compatible. I'm personally a little wary of Reiser though some people swear by it. I suspect xfs and jfs would give good results, too. (Though at one point the jfs people were a little hazy about what their fsync() semantics were.) Larry
