After 7 years, it was finally time to replace my mid-2011 21.5" iMac with something larger and more powerful. The transition to using Adobe Lightroom to process my photos, and the slow performance even when exporting JPEGs from the original RAW files was the driving factor toward making the purchase. It's my declining eyesight that convinced me to go with a 27" iMac over another 21.5" model, not to mention the lack of user-accessible RAM in the current 21.5" iMac.