Negative Ghost Rider. If I've told you once I've told you a million times don't exaggerate
Today's prices from Adorama:
70-200 F/4 L : $615
70-200 F/4 L Image Stabilized (IS) : $1,150
70-200 F2.8 L : $1,335
70-200 F2.8 L IS : $2,130 (version II)
IN 2010 I bought the 70-200 F/4 L for just shy of $600 - which illustrates that good glass never goes 'stale' it just gets better with time.
The good news is that the Canon 70-200 Ls are one of those things that you will only need to buy once
The bad news is that they are expensive enough that you really have to NEED them.
I actually tried to like the F/2.8 version but the rascal weighs enough that I just couldn't imagine myself toting it around.
As already mentioned Canon makes a very respectable telephoto zoom for a lot less money - but speaking personally my 70-200 F/4 L (even without IS) is a wonderment. And yes in low light conditions I'm glad that I've got high ISO settings available and Lightroom for noise reduction...
From Animal Kingdom Pangani Forest Trail last trip.