...one more fluff to Sigma's 18-50/2.8
Sorry to hijack the thread, but...
Of the 3rd party manufacturers I've been most pleased with Tokina but never owned a Sigma.
$400 for the Sigma versus $1,200 for Nikon's 17-55 f/2.8. Hmmmmm... The obvious question is, "how does it compare optically," which I suspect is probably good, but just as important, how is the build quality and mechanical performance? Sigma doesn't have a reputation for high quality construction, but it's not like they're pulling a fast one; they're just trying sell lenses at affordable prices.