I have to admit, I generally prefer a book that is planned out first - or at least restructured after the first draft. Otherwise it can be meandering and have no sense of direction or pace.
a writer with sufficient talent can make a novel or script that is made up as it goes along seem like it was carefully plotted out from the outset. Then there are the writers of Lost (TV show), who can make any plan they might initially have had deteriorate into a great steaming pile of randomized caca...
Arbieroo: We watched a few weeks of Lost when it first came out and then it fell by the wayside. I'd consider picking it back up occasionally, but never really felt the draw.