It spawned too many entities for it.
I would have liked to have seen a more complex level centered around the Icon of Sin personally... The Icon itself being the central piece which you activate about 2/3rds through, and in the completing thirds you run the risk of releasing a cyberdemon and/or pack of arch viles into the mix. I just think if you had never seen it before, and had a level built around it where it was always looming near by, it would be rather intimidating, wondering what was going to come of such a thing...
Honestly, the only game I have ever played that gave me a satisfactory ending was Unreal2. A flawed game with a terrible beginning, but I must say I loved the ending, and actually everything near the end was great.
This got a bit off topic, but its general chat. And a VS/what if thread.