Kowloon, Ascension, and Stadium make it good. Discovery is just there, and Berlin wall is the worst Black ops Map ever.
Kowloon: Kowloon is great, it is now one of my favorite MP maps. It is suitable for a wide array of gameplay styles, although mid-close weapons tend to reign supreme. The zip-lines aren't as much of a death trap as I figured they would be, and they make good ways to flank on objective game modes. The center building with the zip-lines also is a very important place to hold.
Stadium: Stadium is a quality map. It allows for a lot of medium range battles with some close quarters thrown in. I don't really have a lot to say about it, other than it is a really fun map to play on.
Discovery: Discovery is cool, but it just isn't the kind of map you would want from a paid map pack. Don't get me wrong, it is fun. Just not quite awesome.
Berlin Wall: Berlin wall is ,to me, total ****. It isnt the no-mans land that annoys me, but how easy it is to find yourself getting shot in the back. Just typing this brings back bad memories...You may like it, so I wont say anymore about it. But I just don't like it at all.
Ascension: Ascension is the map that made me get back into zombies. It is simply amazing! I love it. It is on the easier end of the zombie maps, but thats part of what makes it fun. Its nice and wide open, and the easter eggs and stuff in it is really cool. I like the addition of the Gersh Device and Matryoska dolls (I know I bombed spelling that). It almost makes the map pack worth buying all by itself, its that good.
Should you Buy it?
If you have the money and you want to put it to good use I recommended this 100% It isnt like the next HUGE thing, but I like it.