Hi there, I am looking at buying the Canon 70-200mm L series lens. I am trying to justify the extra cost of getting the IS version of this lens. My budget is about $800. So my question is, should I get the non-IS version now or save up a bit and get the IS version later. Is the Image Stabilization worth the extra cost? I want to use it for sports photography (mostly outdoors but some indoors) and have a Rebel T1i. Your opinions are greatly appreciated. Thank you.