A lot of people are worried the changes will disrupt the current gameplay. I, for one, think these changes will only make the game even better. Best of all, if Valve implements something that doesn't go well with the community, I have no doubt they'd be very quick to change it.
Valve has updated/patched TF2 more in the past 2 months than EA has done for their entire game catalog in the past 2 decades. I have no fear for the gameplay; the Valve I know will not let us down.