I think the people most bothered by the repetition and "same old/ same old" are folks who've played a lot of Doom and Quake already.
Nah, that's not the problem with the game at all. It just suffered by poor level design and lack of any gameplay depth. The environments initally seem pretty cool but after a while you realize that Delta Lab is no more different than Alpha Lab in terms of look and layout. And the monster enounters offer such lack of variety it becomes numbing.
It's kind of neat for a while and I don't regret having bought it but the best I've been able to do is make it halfway through before becoming too bored to play it anymore.
I thought Quake 4 was a *much*, *much* better experience.
And if you are really set on a FPS for the Xbox then I think Half Life 2 is a much better bet than Doom 3.