If you got one of these with your full-frame Canon body, great news–you can probably sell it for a slight profit. Used copies go for about $600, and that’s about what they cost when included with a kit. Unload it and get yourself a Sigma 24-105 f/4 (for landscapes and general use) or a Canon 24-70 f/2.8 (for event work like weddings). This isn’t an awful lens… it’s OK. But it’s not the professional lens that the red ring and ‘L’ indicator would lead you to believe. It’s very unsharp, especially at 105mm, the image stabilization isn’t as good as other modern lenses, it sucks dust and hairs in so it has a limited lifespan, and it’s not particularly durable. Here are the sharpness charts for the Canon and Sigma, care of DxOMark.com. That bit of yellow on the lower-right corner of the Canon’s chart shows the lack of sharpness. OK, that doesn’t seem like a huge deal, but watch the video above to see just how significant that difference is in the real world.
Here’s a comparison of this lens to the Tamron 24-70 f/2.8 ,which is also vastly superior: https://www.youtube.com/watch?v=QMU1YPO_mXA