I personally think a lot of it is marketing. It matters a little, but not as much as companies would lead you to believe. I don't buy anything according to weight but how it feels in my hand. As far a reels, I focus more on ergonomics and what kind of brakes it has. I love the way a revo feels in my hands, and I love magnetic breaks as opposed to centrifugal brakes. As far as rods, I think sensitivity is getting way too played out. I never have a problem distinguishing between different types of structure and especially bites as long as the rod is graphite, even with rods that aren't as well balanced as some others.
Don't get me wrong, I love spending some money on expensive fishing equipment, but you don't have to.