Seriously, though, what is the RWH authors' plan for tackling the eternal frustration of Haskell book authors, a moving target?
Other tech books face the same problem, which, if they sell successfully and the authors haven't moved into caves afterwards to recover, they address with subsequent editions. If readers find that specific pieces of information have bitrotted, I'm sure we'll hear about it. In that case, we'll create a wiki page with errata, and link to it from the book site.
Just saying, it is worth planning for, especially if the book is going to be successful. I understand if creating that book at breakneck speed has left you looking forward to a break (not of the neck;-), but laying out a strategy for this, and putting it in the preface, might avoid sorrows later. You do have the online version and commenting system in place which you could keep around, you could even keep copies of the precise code versions you use, although adapting the text is more appropriate for this style of book. Thompson and Hudak both have had home pages for their books, but that didn't prevent their readers coming to the mailing lists instead, often frustrated at the beginning of their threads, sometimes disappointed at the end (in spite of a succession of strong Haskell hackers reviving SOE support again and again, there were gaps in between). And your book looks like it is going to suffer more, being completed before, but published after several changes (more base breakup, last time that extralibs come with ghc, haskell platform, extensible exceptions, ..) as well as being detailed and concrete about the use of several real-world libraries/tools subject to normal evolution. Anyway, good luck!-) Claus