Oh, man, I did not want to like this lens. I did not want to spend $2200 on another new lens. But after reading the reviews, I did it anyway.
I already own the 85mm f/1.4 and the 70-200mm f/2.8, so I worried that it wouldn't be all that different from what I have. I was wrong. It separates people from the background better than any other lens I've seen except for the 200 f/2. Almost too much. Backgrounds turn in to solid walls of color instead of details. Environmental portraits don't really tell the whole story since you can't get any information from the background.
I don't often use lenses wide open since they're often kinda soft. The 200 f/2 and now this lens can be used wide open without the fear losing sharpness. The 105 ain't easy to use at 1.4 as the depth of field is measured in millimeters. It's a little slow to focus, but it kept up with a seven-year-old running right at me.
Frankly, I wasn't planning on keeping this lens the first time I used it. I took it out again to give it a second chance, and I fell in love with it. Dang it.