Eye-tracking pros and cons

Just came across this succinct discussion of eye-tracking by Mark McElhaw of Webcredible. He points out the drawbacks of using the technology (from my point of view, the main one is that it can limit users' responsiveness to prototypes, unless carried out as a completely separate exercise to standard user testing). However he also notes the communicative value of heat maps: 'eye candy for senior executives with little time'. His strongest functional claim is that eye-tracking can resolve debates over the effectiveness of alternative web page designs, which can give designers more freedom to try out new ideas. There are interesting discussions to be had, though, when, as is sometimes the case, users don't like the most 'effective' designs.