This will only be a short impressions becuase I don't have much time but I will do a much more detailed version later.

Campaign-Greatly improved story, some actually really sad parts (funny story when MAJOR SPOILER Dom killed his wife it was really sad, but right after that I got a perfect active reload and Dom said S*** yeah (Iwas playing Dom in co-op) SPOILER END But overall you can tell they hired a new writer.Also there are alot more epic scenes and some cool vehicle parts.

Horde mode- Alot like terrorist hunt in RSV2 but better. It is really fun to play with friends or 7 people you don't know. I am currently on wave 30.

Multiplayer- Matchmaking sucks (takes ten minutes to find a game), chainsaw is really cheap, and I just plain suck at the multiplayer. they have a ranking system but it allmost seems like a last minute decision. The good side of the multiplayer is the maps are awsome ( favorite is river) and while it seems like it is last minute idea the ranking system is a welcome addition. (I may only not like the multiplayer because I suck at it but the matchmaking is terrible)