The flexibility to create multiple different icons for each product line that I am working within my agency (iPad & iPhone App development) has been very useful! Not only do you get great looking designs but it's also easy enough if your designer wants some changes or even completely re-designs them themselves rather than going through an illustrator/photoshop process - saves time!! It would be nice when there was more variety between sizes too so they are not just square versions at every size which makes sense considering how much space most apps need these days.. But this isn't really something i've noticed personally yet other then maybe being able use larger images? Great tool overall though especially since its one less app needed before sending out final files etc.