I should note that while I agree with all of the structural advantages of the threadless system, it's not as if a threaded system is highly problematic. And the height adjustability does make the bike a whole lot more flexible than threadeless, and with threadless you need to be careful to not cut too much steerer initially in order to allow you space for future adjustments.
My good road bike is a straight-up racing frame, and I'm now using a Nitto Technomic stem to get the bars to just 4" below the saddle height. And yes, the top tube is long enough.


The 130mm-extension stem (with 46cm-wide bars) is noticably flexy when I stand up and sprint. But if I apply force to the bars perpendicular to the frame and rock the bike side-to-side instead of torquing on the bars relative to the frame (there's different ways that you can apply force to the bars) I can hammer pretty well without flexing the bars much. And I'm comfortable trusting a forged Nitto stem.