Also, you should be able to tell by the message you get when you turn in the token whether or not your faction is increasing. It'll either tell you your faction has gotten better, or it'll either not tell you anything or tell you it can't get any better this way (this message is used with faction caps killing giants/dragons, not sure if it is with quests or not).
From what I hear, a stack of tokens may very well not take you to the next faction level. It seems to take a LOT of tokens to make any significant impact.