Ease of use, it allows you to set up your own pool if required. It's free so there are no catches which sometimes can be an issue with some clients we have used in this space previously such as Hashflare! There isn't much about miners using easyminer that I do not like but nothing comes out loud at least yet :) My experience has been mostly good however occasionally one site will give me trouble when setting things back how they were - maybe due just being unfamiliar? The GUI looks nice although my graphic card does need more RAM :). If someone wants something simple then go ahead otherwise try several others until yours fits what most people want/need from their miner (i think i know mine pretty well now!). We run multiple sites across different virtual servers all hosted by our hosting provider who provides us web server instances via Amazon AWS EC2.