I've decided that instead of posting the full actual play results here (they're a bit long to read on a blog), I'll only post the design notes and what I've learned from the session (a recap) rather than the full post. Those I'll throw on the forums, where they are easier to navigate and read.
That said, the two sessions I've run so far have shown me several good things about designing only what you need as you go. By leaving a number of entrances into the dungeon from other places, I can create any number of means by which others entered, and I can leave all sorts of dangling plot hooks for later.
I also see the huge benefit of actually play testing the adventures you design; you learn all sorts of cool little things once you actually pick up dice and play it out.