If you can get past the cost of this add-on content, AND play MW2 online frequently, then you should consider this.
There honestly isn't too much to say about the maps, because that's all they are. New maps for Modern Warfare 2's multiplayer. It adds a small bit of variety to the game, but of course changes nothing else as far as gameplay goes. They will soon feel like just another small part of the game. Another small part of the game you have to pay for. To get to the point on deciding whether to buy these maps or not... As said in my intro if you play this game online a lot, you'll probably want to get this, or at least consider it. If you can get past the $15 dollar pricetag, you should just get this, not that you have to. However the new maps do appear quite often in the normal playlist.
But more about the maps themselves. There's Bailout, Storm, and Salvage... as well as Overgrown and Crash from Call of Duty 4. Overall in my opinion they are decent maps... decent. The 2 original Modern Warfare maps do bring back some nostalgia to anyone who played that game. Here's a quick summary of the maps and my opinion on them.
Bailout- an interesting level with a chain of buildings and many areas to run around and go to. Definitely some popular spots, a few of which for sniping. One of the better maps in the game.
Storm- as the name suggest the map is in a stormy environment. Revolves around a large warehouse typed building. A little confusing of a level overall. Many places to hide or flank. My least favorite of the 3 new maps, but it's playable.
Salvage- a mostly flat and snowy map (hehe that kind of rhymed) with very few places to hide. Rather small in size. It's pretty much a snowy junkyard with pipes very similar to the ones in Scrapyard. There are a few perches for people to camp on, but I think it's an easier map to play on. Probably my favorite new map
Overgrown- one of the new maps from Call of Duty 4. Definitely a popular one from the game. Typically more snipers on this map. Many small buildings to run around, and a few big open areas. Many ways to play this map.
Crash- the other map from the first Modern Warfare. A few high points, and overall a somewhat small map. Great for flanking.
So there's my take on the maps. I gave it a 6.5 due to the amount of content you get for what you pay. No other changes for actually buying this. The amount of time played on the new maps might eventually make this seem worth it. But with another wave of maps on the way, it might be worth giving this one a miss.