I was wondering if it is that sensitive that the slightest movement when taking a picture with out the IS will show blurry....will you ALWAYS need to have a tripod for a bigger zoom lens that does not have the IS?

Everything depends on the shutter speed when you take the photo :)
If it is very sunny, there is no problem taking a photo with a long zoom as you might still get a speed of 1/500s per example.
Now if it is not very bright, and if the speed is around 1/30s even after increasing the ISO, then a stabilizer or a tripod is needed.
With the Canon Pro90IS and its image stabiliser I managed to take good photos even at 1/15s at full zoom (370mm)!

Better than image stabiliser is getting a fast lens (like f2 or f2.8) but they are very expensive.

Olly

Thanks Olly, I was lookiing at the canon 70-200 L f4.0 usm.....some say ok with out IS, some say not....which I guess comes back to the speed and light factor again, right? I wouldn't then have the option of the faster lens.

which I guess comes back to the speed and light factor again, right?
Right :)

If you get the Rebel XT, you can use high ISO without degrading too much the photos so it helps if you do not have an image stabiliser.
That 700-200 f4 is an excellent lens (great quality for value) and not heavy.

Olly