At the risk of starting a brand debate, I am wondering about a new lens... I'm working with a D70 and keep getting asked to do formal portraits. I have the lens the kit came with, and I have a 50mm f/1.8, but that wouldn't work for weddings when I need to move around. My question is, should I pick up the Tamron 28-75mm f/2.8, which I can afford now and use now, or wait until (or if) I can afford the Nikkor 28-70mm f/2.8 someday down the road? I hate taking shots with the less sharp lens I got with the kit, but I don't want to put down $400 for a lens I will wish I hadn't bothered with. Anyone have any experience with this or know of another lens that might be more worth my dollar? I'm a portrait and special event newbie photog and now have a couple of weddings in the near future to shoot. Can anyone offer advice?