Yesterday I beat the game in God mode.  It wasn't as hard as I thought it would be, but it had it's tough spots, specifically the parts where Kratos is ridiculously outnumbered.  Other than that, it wasn't too bad, and the bosses didn't give me too much of a hard time either.  My final time was 9:40, which is 10 minutes more than my run in Spartan Mode.  After I post this bulletin, I'll probably start the game on Titan mode, the hardest difficulty yet.  I can see it now...PS2 controllers will be thrown and foul language will be yelled out in utter frustration.

On a side note, I just finished Challenge of the Titans, which consisted of 7 rooms, each with different objectives to complete.  It was pretty tough, but I got a Titan ranking on all but one of the challenges.  I unlocked Arena of the Fates and a bonus costume for Kratos, as well as some cheats.