Yeah, any lens is a compromise max aperture/ constant aperture / zoom range (or not if a prime)/ price / weight etc. You have make sure that you've selected a lens that meets your needs for these factors. The 15 - 85 meets my need for a walk-around lens - that's why I like it a lot. I would use a prime for portraits. That's why the difference of opinions on these threads. Gotta choose the right horse for the course. Folk are often talking about different courses.