As far as over rated, I think any big hype, big sale products. Stuff that is "on sale" when its been reduced to a price that is actually what the company wants. Every product from the Favorite brand seems to be made out of pure advertising and hype. Duckett products are all expensive for chinese rebrands. Shimano's high end products are amazing, but ridiculously priced. I have owned many stradics all the way up to a stella and dont notice a difference. Abu garcia reels are a joke, all made by doyo and I destroyed a brand new ambassadeur c4 last year by doing absolutly nothing wrong. Abu's low end tho is amazing for beginners. St-croix rods, depending on the series, get heavy and not so sensitive on their bigger rods. G-loomis rods are way overpriced, but sadly worth it.
Under rated, most solid lower end reels from many companies are actually great, okuma ceymars, abu black max, shimano caenan, daiwa revros, pflueger reels etc. As far as rods go, okuma rods are really nice for the price, to bad the reels dont follow... fenwick HMGs and HMXs are not uber expensive and are a real nice rod. I find daiwa tatulas xt are also cheap and reliable good rods nobody talks about. But as a go anywhere cheap rod to me the most under rated rods are the okuma ceymar, abu garcia vengeance, fenwick eagle, shimano slx.