I try to keep things simple. Stitched panoramics are relatively easy if you make a point of carefully leveling the tripod first; then sequential images don't stair-step from one to the next. The longer your focal length, the easier it is to stitch frames together. With the 70-200 zoom, parallax and distortion are generally non-issues. With the 24-70 zoom it helps to rotate the lens around its nodal point, which is simple to locate. Choose the focal length you need; then use a tape measure or ruler and measure that distance forward from the image plane (helpfully marked by Canon with a little circle & slash symbol on the left side of the pentaprism) and that's your nodal point.
I confess that I just stitch manually in Photoshop. I tend to overlap successive images by 30% or more to make alignment simpler. It's critical to expose in metered manual mode, so each frame has the same aperture and overall exposure. I bring each successive frame in as a new layer at 30% opacity and nudge it over until it's aligned properly. I then use a soft eraser to smudge any evident joints. This has worked fine even for images stitched from two rows of four images each. I save one copy with all the layers intact for future rethinking, then flatten the file to make it more manageable in size for subsequent image editing.
As for horsepower, more is always better. A 22" x 64" image at 240 dpi is something over 500 megabytes. I have a 3.2 mHz Pentium 4 with 1.5 gigabytes of RAM, and I get to watch the hourglass symbol for a while after hitting "enter" for most operations, but it's not intolerable. Once you're done with gross exposure adjustments like levels or curves you can drop down to 8 bits per channel to make the file smaller if necessary, but I usually stay at 16 bit. The most time-consuming part is the actual printing. A 22"x72" print takes just about an hour to come off the 7600, set to 1440 dpi and "high speed" turned off. (I figure, why do anything to compromise on quality after working so hard to acheive it?).