I'm about to order a nicely discounted base 27" late 2015 imac - it comes with a traditional 1TB HDD 7200 drive. The fusion drive - with it's tiny Solid State portion adds $200 to cost. Seems like too much - I'm coming from a PC where I put in a huge SSD drive for that amount. I'm like to be as frugal as possible - and order the traditional drive machine now, and them upgrade it to a nice big SSD in a year or so. Anyone see any issues with this approach?