Just had an email letting me know of the first major review of yWriter 4.
Lots of pros, a good score, and only two cons. One of the cons (no submission tracker) is irrelevant, since I already have Sonar in the stable. The other ... well, I don't believe in hand-holding when it comes to software ;-)
Anyway, take a look at the review for more.
EDIT: Don't miss the new yWriter mailing list.
Simon Haynes is the author of the Hal Spacejock and Hal Junior series (Amazon / Smashwords / other formats)