Has anyone had experience with the Sigma 18-50mm f/2.8-4.5 (not to be confused with the 18-50mm f/2.8 lens)? I'm replacing my Rebel XTi with either a Rebel T1i or a Nikon D5000, and I'm wondering if this would be an upgrade over either kit lens. I have only found one detailed technical review of it: http://www.slrgear.com/reviews/showproduct.php/product/1249/cat/31 But I'd like to know if anyone has any practical experience with it, and if so, what kind of shots you've taken with it. Long story short, this was not a planned upgrade, so I'm not looking to spend a whole lot. I'm almost tempted to just get a 24 or 28mm prime lens, since that's about the range I would generally use with the Canon kit lens, but I'm afraid I'd end up missing the versatility of a zoom lens. So perhaps a better question is: What is a good multi-purpose lens for around $300?