I've lived in a block house (entire structure) for four years as a renter and just purchased one of my own. I don't think that they are cheaply made--they are great in the summer because the walls are actually cool to the touch. I can be outside in the heat and walk inside my house without the air conditioner on and the house feels 10-15 degrees cooler. A bit cooler in the winter but I've yet to have a winter in the new house, so it could be different.
Aesthetically, they're not the best, but we had the interior walls covered with stucco and it livened things up a bit.