Want lens for: outdoor sports. (99.9% daytime/mid-day). horse racing, surfing (200mm is a little short for surfing but I go on the pier to get closer shots) and whatever else I may want to shoot. I am looking for an upgrade to my 70-300mm and I have been looking at the 70-200 lenses for quite awhile. I wish I could get the 2.8 IS but that is just way too expensive right now ($1900?). I said okay Ill get the 70-200mm F/4 (non-IS) for $650, then i started looking at the two mid-range ones (f/4 IS and f/2.8 non-is). I then started to want the F/4 IS because I wanted the IS but now that I think about it, I dont think ill ever use IS except for panning, but not actual low shutter speeds. The focal length is too long for what I would use in-doors. The F/2.8 would seem nice, as I just can use a faster shutter if it gets a little cloudy and require a faster shutter for daytime sports. I do have the XTi and the ISO performance is really bad. I dont even use 400, just 100-200. Not sure if that helps me decide 2.8 or IS. weather sealing isnt an issue as I dont shoot in that kind of weather, nor do I have a weather sealed body. The 2.8 is heavier but Ive hand-held the 2.8 IS in-shop and I dont mind it much. F/4 non-is came out in 1999 and IS version ins 2006, any optical quality changes during that time? Is the only real difference IS and weather sealing? Everyone says the F/4 is sharper but I can stop the 2.8 down to F/4 aswell to get sharper. The 2.8 non-IS came out in 1995! Thats like 15 years ago, think canon will update it? (I wont be able to afford the updated version anyway haha) So the IS versions are newer and weather sealed while the non-IS versions are older. Does this really matter much? I know lenses last awhile. Im so in the middle of things I cant make up my mind!!! maybe someone can give me some insight... FYI, it will take me awhile to save up but I plan on getting 70-200, then 24-70, then 100-400 Also I kind of liked the idea of 2.8 cuz it has 77mm filter size and so does the other lenses i listed above (i think?) So I could share a CPL between them. But that isnt a huge decision maker.