Yes, I find that having no caffeine at all improves my average overall alertness, almost completely cutting out the highs and lows, both. However, I really like the hyperalert state that caffeine brings, and I don't know any way to get it without, so I put up with the lows that accompany it, going off caffeine every year or so for a few weeks to reset the effect (which gradually wears down so that the hyperalert state approaches mere alertness).