He plays almost the same as Mega Man, except he can slide and charge his blasts, which apparently Mega Man cannot do in the Mega Man 9.
Proto Man can also deflect most bullets with his shield, besides the larger blasts which will still hit him and push him back, and also interrupt his charge slot. All Rush adaptors are changed to Proto adaptors as well.
Hit the jump for two tiny development screenshots. [GamesRadar]