Full power is more dramatic than that :-).

My experience is that if someone begins "Well, yes" rather than, say, just "Yes", their intention is generally something less positive than simply agreeing with you. ("Well, yes. What kind of idiot would need that to be said explicitly?" "Well, yes, but you're forgetting about X, Y, and Z." "Well, yes, I suppose so, but I don't think that's actually quite the right question.")