Are Ipoh and the Cameron Highlands worth the detour?
Ipoh and the Cameron Highlands work best when you want a slower inland layer: food, old streets, caves, cooler air and tea-country scenery. They should not be added just because the map between KL and Penang looks empty.
Answer
Ipoh and the Cameron Highlands can add useful contrast to a Malaysia route, but they are not automatic first-trip essentials. Ipoh is stronger for food, old-town texture and a gentler pause. The Cameron Highlands offer cooler air and tea-country scenery, though traffic, weather and overbuilt pockets can blunt the romance. Together, they work best for travellers with enough time to enjoy the detour rather than rush through it. If you only have a week, KL and Penang may deserve the focus. If you have longer and want a break from heat and big-city movement, an inland pause can make the route feel less obvious.