The zip side panel is what sold me — I can load my daughter in without wrestling the whole cover off. It folds into that mesh bag small enough to leave in the undercarriage, so it's always there when the sky turns.
Kept my toddler completely dry through a 20-minute walk in a downpour, and the cover still fits neatly in the mesh bag when we're done. The zip side panel makes loading him in way less of a wrestling match too.
The zip side panel makes loading my toddler so much easier than wrestling with a full cover. Only gripe is the mesh storage bag feels a bit flimsy, but it still folds down small enough to stash in the wagon basket.