The Feature has an interesting interview with Erik von Hippel (whose latest book Democratizing Innovation can be downloaded from his website in PDF format or bought from Amazon). He researches the contribution to technical development from lead users.
The interesting perspective here, of course, is that users (or, at least, customers) can lead you astray when you are facing a disruptive technology – and, at least according to Eirik Chambe-Eng in Trolltech, you cannot expect applications to “write themselves” in an open source model, only error checking and comments on extensions.
Looking forward to reading this book – the difficulty of using leading users must lie in when not to use them.