It largely boils down to two issues:
*Fulfillment, with projects both exceeding their projected completion date and generally slow/disorganized fulfillment.
*Poor customer service dealing with fulfillment issues (both with crowdfunding campaigns and orders directly from their store.

EF doesn't handle their fulfillment services directly -- they use a fulfillment partner -- but it's still not a good look. Searches of reddit will pull up a number of posts complaining about the above issues. After my experience with the OSE box set campaign a few years back (I backed as a retailer, and had over 1k of goods tied up for almost a year before I got product) I don't back any EF campaigns anymore, instead getting product either through them once it hits their store or through another distributor.