i've got an XT and only the kit lens right now, and i'm thinking about buying a new lens for it. I was wondering if the EF 35-135mm f/4-5.6 USM was a good lens to buy as a first lens. i'm also considering buying a 50mm f/1.8, but i can't buy both at the same time. which one would you guys say is a better first purchase? and how is the overall quality on the EF 35-135mm f/4-5.6 USM?

