Australia's PALGN has posted a review of Freeverse's XBLA port of Marathon: Durandal. Their verdict:

Marathon: Durandal is one of the best value games on the XBLA. You could spend more time playing through this than Halo, and at a fraction of the cost. There are aspects of the game that are archaic and it’s not a good game in short bursts, however, it provides a mysterious and lengthy experience for anyone who is willing to immerse themselves.

They did say it's too easy to get lost, but there's always the Marathon Spoiler Guide if you do.