equipment recommendation - Do I really need a wide-angle zoom lens?

I have a crop frame canon DSLR and currently have the 18-55 kit lens and the 50mm f1.8 II.

I love to travel and mostly take only landscape photos. Up until I became a stackexchange reader, I believed that a wide-angle zoom was a must for landscapes. I've since started thinking otherwise but I am not completely convinced.

I know I could use the widest length of my kit lens for landscapes, but I am not completely satisfied with the results. The images are not sharp despite using a tripod and f8.0. And the colors are no-where as good as the result from the 50mm.

I've been looking at picking up the Canon 10-22 for a while now. But it would mean parting with a significant portion of my bank-balance. I need some more convincing in whether I should or should not pick up this lens.