I made it through the GoW2 campaign on hardcore after a marathon session yesterday and managed to bump my score up by some 220 points in the process. Overall I have to admit that I like the storyline (some fantastic & funny cutscenes), but some of the new elements need tweaking (i.e. rear targeting on the Reavers), plus the lame platforming(ish) worm escape and the end boss battle are weak. However, the improved enemy AI more than makes up for these minor faults.
I also like the idea of being able to ride the Brumark & Reavers and drive the Centaur tank, but it copies Halo too much (i.e. ice breaking apart just in front of the tank just like Halo3's Warthog escape finale). Then there's the unanswered questions (Locust Queen & Marcus' father) that set up the final installment of the trilogy. Let's just hope that we don't have to wait another two years for the conclusion, which seems likely with Halo ODST set as next fall's major Xbox release.