Hi guys. Yet another lens question... I know. I own a Rebel XT and am seriously debating between the 70-200 IS and the 70-200 non IS L series lenses. I mainly want this lens to do portraits with a choice of varying bokeh and the ability to shoot in low-light. It sounds phenomenal from what I hear and the zoom range is perfect. Will I need the IS though? I mean, portraits are basically always shot with a tripod and I have a Manfrotto 190PROB. I can understand indoor sports shooting and such where you might be shooting handheld and the IS would help. I will also use the lens for isolating some scenary shots and things to that nature. Is there any difference whatsoever in the image quality between the two, or the construction or lens elements? Thanks in advance, you guys are always a great help.