I'm really thinking seriously about a Sigma 150/2.8 HSM. I've been convinced by threads here and reviews elsewhere about the macro capabilities of this lens. However, I'm also really thinking about a 180/2.8. Will the Sigma do an adequate job as a mid-range telephoto or will I need to acquire another lens to fill that role. I'd love to hear comments from users about focus speed and accuracy when you're not shooting little bitty things... Thanks everyone!