Thanks for all the interesting comments! IF certainly isn't a great metric but it is one of many that selection committee may consider when evaluating CVs and many people do include them on their CV. Basically use want ever metric makes your CV stand out and this may differ depending upon the stage of your career. It is really about emphasizing your research impact in the field you work on to a group of people who may not work in that exact field. As an aside: in NZ we have a performance based research model of funding (PBRF) for tertiary education organisations, ran every 6 years - in which we are required to include IF, H-index, journal ranking etc as part of the "Quality Evaluation" of your research. Which means there is now a bit of a drive for University departments to employ people who will rank highly in PBRF = more $ for the Uni.