Been a COD fan since WAW in case that matters to you.
1. Campaign is only comparable to the first MW(not cod4) and is inferior in almost every way. (Missions feel unimpactful and short or gimmicky and drawn out) the last mission is absolutely terrible just a heads up
2. Multiplayer has a ton of progression so if you like the flow of LAUNCH MW you will like MW2. (The maps are absolutely terrible) it reminds me of MW launch when everyone left maps as they spawned in and waited til DLC maps dropped.
3. Further the point (Maps are absolutely terrible)
4. Gun and camo progression is new and pushes you to use different subclasses of the same weapon to level and unlock customization for the archetype. (I like this change)
5. I do feel like the multiplayer (while it leaves a lot to grind for) is in a similar place to the first MW at launch.
As in it feels grindy and unrewarding but also promising as you know dlc is on the horizon.
If you are a COD fan I believe this game will be fun for you increasingly as the seasons progress. If you are expecting a continuation of MW (RIGHT NOW) you are not going to get it. This game has a FAR worse campaign to the original and Id say a on par or even multiplayer to the original.
If you like COD for the long run its worth the buy. If you are buying for simply the campaign it is not worth your money.