Originally Posted by spearfish25

One thing to keep in mind is that your shifting and clutching speed should be proportional to the rate at which you're accelerating.

For example:
If you're driving away at a leisurely pace and going up through the gears, the smoothest shifts will be relatively slow clutch depression, gear shift, clutch release.

If you're 'on it' and revving quickly to 5k+ rpm, you'll have to clutch, shift, and declutch much faster to have a relatively smooth shift. Realistically, you have to be lightning fast to have no forward-backward forces during rapid acceleration. Just imagine you're being forced back in your seat while your foot is flat to the floor in second gear. You hit 7.5k rpm and depress the clutch. Boom, you've lost your acceleration and you sense a change of momentum wanting to throw you forward. Now you complete your shift and you're back on the gas full throttle. Wham, you're back into the seat accelerating again. If you shift very quickly, you minimize the forward-backward throws.

When accelerating slowly, you don't have much change in momentum as you change gears and a slow clutch, shift, declutch makes for a smoother transition. Try it yourself. Accelerate very leisurely but then try to shift as fast as you can. I bet you grind the gears more often than when you shift quickly while you're accelerating rapidly. It's just natural to match shifting speed to acceleration rate.