Well, I've beat every GoW game on Hard difficulty, but in CoO and GoWIII, I could never get past the very end on God/Titan/Chaos. I would get so far and then, there would just be way too many enemies to deal with. In CoO I got to the Temple where Kratos is seeing his daughter, and in GoWIII, I got to the very end of the Labyrinth and I couldn't get past last huge fight. I believe I got past it ONCE, but the Hades Cerberus (the one that spits out baby cerberus') and the Satyrs. And there wasn't an autosave point there, so I always had to restart in the Labyrinth.
But I have completed all the challenges on all the games (excluding the GoWIII DLC challenges) and platinumed GoWIII. Haven't had enough time to replay the first two games thoroughly on PS3, and I already beat them on Ps2. I am the best GoW player I know. I can pull off wicked-sick combos, yo! (That last part was a joke).
I like the idea of promptless mini games but I just think we have too much time to react to their attacks. On this note, there were alot of times in the 30 min SP demo that I was frustrated watching things move in slow motion when they should have been in normal time. For example, when Kratos jumps off one of those big monsters and starts sliding down a hill, why show that in slow motion?
You'll probably have less time on the harder difficulties. That would be awesome.