Very true. Obviously you want to also choose a reputable roofer who will install them properly. In high wind prone areas, a proper nailing pattern is critical to keep the shingles on the roof. Yes, here in the south we deal with heat and hail storms.
Your point about ventilation is critical as well. A roof that isn't properly vented will not last nearly as long as the warranty claims. I highly recommend a continuous ridge vent if it fits your application.
If I do a metal roof on my next place, I'll probably go with a light color to cut down on the heat. We're going for a farmhouse/craftsman look so a light color roof will be architecturally appealing anyways. I'd really love to do a cedar shake roof but that's $$$ for install and maintenance.
Also, if you're worried about the sound of a metal roof, it's really not as bad as most people think. Most people think of a noisy barn roof but that's not really the case when you have a layer of roof decking in between. In additon, a layer of poly-iso foam board will help deaden the sound and really isn't that much more of an incrimental cost in the big scheme of things.