I always handled my gear well, whether it's because of the delicate finish (like the HD600) or because the build quality doesn't inspire confidence (most Grados). I dented one of my gymbals once because I packed hurriedly after a meet, emailed Grado to inquire how much for one, and they sent me a replacement free of charge.
That said I still think they should come up with better parts, specifically the slider. I really think that shouldn't be sliding around too much; maybe some sort of stopper to keep it easy to slide but be able to lock it into place would be great. The plastics I can live with, except on the 325 - the gymbals should at least match the cups or be close enough in color.