This lens is the cheapest "L" lens from Canon. Anyone who wants to come into such a pleasure / noise, for it is the first point - there is nothing to regret.
Sharpness is 1a, the autofocus is wonderful (even I, who focus manually point to 85%, to the finishing touches still rauszubekommen) use it.
I can only confirm, even every layman recognizes at the handling of the lens and at the most Henden end image quality, the lens is very good - logically better than any non-L lenses.
Ok, there is no image stabilization available. But what does that mean? This means that you can not shoot at 1/15 sec shutter. But nothing more. If you have a tripod, it will take, and then go even the 1/15 s. The lack of IS just means that you need more hochschrauben the ISO in low light conditions that to make sufficiently short exposure times. Or you put the lens on somewhere and do not care.
I write not because I do not begrudge their IS all IS-owners, but because I did not hesitate even before buying precisely because of the lack of IS.
I stood between the election of the 70-300 IS with no L and this lens here. Haptics, image quality and autofocus but have triumphed (have also had the 70-300 in the hands).
Who is accustomed to non-L lenses, may wonder what you still can do sooo much better. Please, try it out, it's really really a noticeable difference, even independently of circular red status icons :)