It slows the game down because it is one more thing the GM has to control. If the player can place the fireball or the monster where he wants it, instead of telling the GM where to put it, or have to wait for the GM to give control of the token to the player it would be faster. It is no different than if we were playing on an actual table, and the only the GM was allowed to move the player's summoned monsters.
"Hey GM move my monster over there beside the goblin with the axe, but to the left of the kobold."
GM moves the monster
"No the other goblin, the one I pointed too"
Gm moves monster again.
"I wanted him to flank"
GM--"GRRRR"
I am sure me trying to tell someone to do something is slower than if I do it myself.
I am a GM, and letting the players control token will also help with area of effect spells once I find some tokens to represent them.
This is *extremely* hyperbolic, Adrian. Once a token has permissions set, the token can be copy and pasted to any given Page and the permissions assigned will be kept intact. At the beginning of a campaign, set up your PC's tokens, their familiars and spell templates on a blank Page. Apply the permissions to them and then you're good to go. All you have left to do is copy and paste them in whenever your PCs need them. Once they're on the page, your PCs can take it from there.