Kin - with regards to the lens that you suggested, I was looking at obtaining the 75-300mm IS lens that is available. Do you have any experience with that particular lens and do you think it would be an appropriate step up from what I'm shooting at now?
Also, I've started shooting in the "AV" mode and it has cleaned up the noise that was present previously. The other thing that I like about that setting is that it automatically sets the TV mode which is great when shooting moving objects. Finally, with regards to ISO - isn't being at a lower value (100) better when shooting in the bright midday sun?
Be aware that there's TWO different Canon IS lenses in that range, the older 75-300IS and newer 70-300IS. The 70-300IS is the better one by quite a bit. As a regular lens for general shooting, it's fine. At about $799 (Henry's), if you want to get into more wildlife shooting, I'd lean towards something longer. I had recently picked up a another used Sigma 50-500 for less than that (now my wife has one, and I have one). I see many Sigma 170-500's going on clearance also for less than that (Henry's & Ebay).
As for shooting at lower ISO's, yes, typically the lower is better, except that most dslrs don't have a true ISO 50 mode, so don't bother with that even if it's available.
With longer lens, you pretty need iso 200 or 400 to keep the shutter speeds up.
Except for rarities and lifers, I typically don't bother shooting during the midday sun. The light is just too harsh and ugly. It takes too much work to get good images due to harsh shadows, blown highlights etc. Mind you, with fall and winter well on it's way, "midday sun" is not much of a problem