a very large zoom

I hesitated between 7The 70-200 IS f / 2.8 and the non-stabilized 70-200 f / 2.8 because I wanted it to be usable in low light .... if you are not in this case, the 70-200 f / 4 is more than enough as it is excellent.
although the price is a problematic element, think that you retain all your life ... as they say .. the boxes pass stones (goals) remain! and I am not at all disappointed with my purchase.
It really is perfect in low light environment (church, event, etc ..).
Not need the flash ....
stabilization is imperative if your box (mine is a 60D) mismanaging the rise Iso. it is no longer even if your case is a 5D Mark III or 6D ... you can save 500 or 600 ... but as long as invest, take this option!
Because even at high ISO speed can be limited to the stable release. Indeed, if you go up in ISO you increase your "light" which can be disabling if you do not want to rework your photos CS Dxo or LR. Yes, increase the ISO speed to use a very fast installation time and eliminate the risk of image blur .. but you lose the ambient light if you are in Jpeg!
unlike writes STEPHANE B .. (sorry Stephen!) who writes this:

[Now if a longer exposure time is required by the circumstances of the shooting or the intended effect it is obvious that the tripod will be required but I would answer this objection, on the one hand, there safe bet that even with the stabilized version of the use of the tripod will be necessary and, on the other hand, if one wants to sérieursement of the photo, invest in a tripod is not really a problem.]

when using a tripod ... you have ABSOLUTELY disable stabilization!

Me, I have a 60D .... I tried again to take pictures this weekend without stabilization therefore without Is .. (chili festival in Espelette, in broad daylight, under the sun, F8 to F11, 100 Iso 400, 100 to 200 Focal ... well 85% of my photos are floutées..et are many camera shake!
as soon as I stab reactivated, 98% correct!
There is no picture! in the case of say ... it is absolutely the 70-700 f2.8 with IS on boxes that are not in the high-end boxes ..this is to say that prices> 1700 -2000 .... FYI, my 60D is still commercially .. and yet it was worth starting in 1500 .. but is not able to manage without the 70-200 IS.