The release version of DragonFly has been brought to 1.4.3 to incorporate the recent Sendmail security update, among other things.  Bleeding edge code has been brought up to version 1.5.2, because Matthew Dillon has added (after the bump) his potentially destabilizing BUF/BIO code.  If you like running Preview, update and plan to stick with it a while until this new technology gets sorted out.