The new rebel is great! My intern just got one. I can't believe you can get such a good camera for such a low price. Amazing! I wouldn't mind having one just for the 1.6x multiplier. It would turn my 70-200mm into a 112-320mm f/4. I can buy a new rebel cheaper than a 300mm f/4!
f/2.8 is useful on the telephotos because it let's you run a shallow depth of field. Great for portraits because you can blur the background. You can also run a faster shutter speed which is very helpful for action photography. Oh yea...you can shoot in low light better, it focuses faster in low light and the viewfinder is brighter also.
f/2.8 lenses are not always sharper than their f/4 counterparts. The new 70-200 f/4 IS is just as sharp at the f/2.8 and is a lot lighter in both weight and price.
Wide angle lenses have such a large depth of field already that you really only get a one stop shutter speed advantage using f/2.8 over f/4. You can get the same shutter speed at f/4 using and the next highest ISO setting. Nowadays the cameras are so clear of noise you can run up to ISO 800+ with no problems (unlike film).
Any of Canon's EF lenses are super sharp.
I always use a tripod and cable release when I work. Except for portraits or fun it's not worth taking the chance of a blurry photo. Tripods also force you to take more time and think about your composition.
I wish I could send you the link to my website but I have to keep my identity secret for obvious reasons.
Good luck with school! It must be starting soon. My intern is out of here in Aug to study photography in Utah. Part of his internship was trimming my bud
. He gets all the bud he can smoke!!! He doesn't know it yet but I'm sending the phat bag of blueberry with him to school! He's stoked!