I got the new map pack thanks to the Season Pass and would like to share my opinion on it.
Wreckage is too brown for my liking, but the skybox is excellent. However, while the gameplay is awesome, it's the worst of the 3 maps.
Shatter looks amazing, and plays amazing. The gameplay is really smooth here and there are plenty of places to flank your enemy. Good for big team objective types.
Harvest is better than I thought it would be. It's good for smaller team games such as 4v4 slayer and King of the Hill. A really good map.
Overall the Crimson Map Pack is a brilliant start to Halo 4's DLC run, and can't wait for more. Hopefully there will be smaller arena maps.