I like the system and the best part is you can try again later on when your speech is higher, now granted that won't happen all the time quest rewards are a one time thing
Not always unfortunately. Some checks are in unique dialogue paths that can't be reinitiated. Just a heads up.
@above:I found you can get most general checks around 50, 65 for a few advanced checks, and 75-80 for the rarer hard checks. I never needed 100 until the very final encounter, but it doesn't do anything except give XP....which is useless at that point.