Although it doesn't have IS, I really liked this lens when I borrowed it from Canon.
However, I'm still trying to decide if I really "need" to have it.
It lacks image stabilization, and it is pretty heavy.
BUT, it's much sharper than my Canon 24-105mm f/4.

There are Third Party (less expensive) f/2.8 lenses that cover the same range and do have image stabilization. Unfortunately their IQ isn't the same. IQ would be my main reason to lay out $1600 for a heavy lens without IS. So I remain undecided.