Vigil general manager David Adams explains in the demo's announcement that the dev "really wanted to give gamers a true idea of the variety of gameplay that the game offers," adding, "rather than just making a standard 20-minute demo version of the first few levels, we decided to give away this massive level and reveal the true essence of the game."
Here's what we want you to do. Bookmark this post, then, once the demo hits, come back here and leave a comment letting us know how long it took you to complete. Nothing official-like, but it'll be fun to put THQ's estimate to the test. Just remember -- it said "for the average player." We know you're all well above average.