Recently at the office a fellow co-worker of mine got a french press. I see that he slowly plunges the grinds down to the bottom as the roast brews.
Does this really affect the flavor of the coffee?
Plunging speed will only change the flavour in a minor way. Plunging slowly/carefully will prevent more sediment from getting through the filter as you push it down. Change in amount of sediment in your cup will change the mouth feel of your coffee, and may influence the flavour a little bit. I.e.: If there is too much sediment it may be more bitter.
I have found I do not even need to plunge at all when making French Press, I have started simply carefully pouring the coffee out through the filter without plunging.
Link to cat video performing the French Press method described above.
See answers to a previously posted question on this topic as well!