Greetings,
I'm looking around for a new 100-300mm range zoom lens. Currently I'm using the EF100-300 f4-5.6 USM. I think I've outgrown this lens as I begin to compare it to my prime and L lenses, it's quality is lacking behind them. I read of good reviews of both the Canon 100-400 IS L and also the very affordable 300mm F4L. Then I came across this Sigma 120-300 mm F2.8. It is a bit expensive but this is the fastest around. Of cause there is the Canon 300mm F2.8L but it costs much more. Any comments...

IMO the only drawback with the Sigma is its weight, I thought the 100-400 was heavy until I got the 120-300, but there again its f2.8 and therefore has a lot of glass so you expect it to be heavy, I would have liked IS with it though

