As a big Warhammer 40k fan, I played the stuffing out of Dawn Of War 2 and loved it. Chaos Rising was very dissapointing. All it does is tack on 10 extra levels, another character, and a good/evil system which has ZERO effect on the story until the endgame cutscene!
There is barely 1–2 days' worth of playing in it, and some of the maps in single player are literally the same maps as were present in the original, only rotated so you don't notice.