Pros:

Good map, if playing with music.  

Cons:

I don't know why the author bothers to update this map anymore, because no one will play this newer version if they have the version with music.

Conclusion:

This review is for all versions of the map without music.  It basically cuts the enjoyment in half, so I'm giving it a 5.  Sorry.

Pros:

Excellent, well balanced campaign that is exciting.
Artwork is good and maps are realistic
Challenging as needed with great ups and downs
Great level design and feel of the entire campaign
A classic custom map of Left for Dead that everyone should play.

Cons:

This map conflicts with poorly converted L4d1 maps or maps that are not built well.  So far, I have found that it conflicts with the strangely popular yet poorly made Cold Case map, as well as the Lambda map.  Both maps are uploaded by Herbius.  Be careful when downloading his maps (his name is not the author name, but the uploader name). 
If a map conflicts, it must be removed from the addons folder entirely.  It is not enough to un-check the map from the internal add-ons manager.  It must be removed from the folder entirely.
To date, every map that has conflicted with IHM2 is worth being removed.  Cold Case and Lambda are easily sacrificed in order to keep playing IHM2.

Conclusion:

Overall, this is an excellent campaign that provides a lot of fun.  I've played it numerous times single-player and multi-player and have never stopped enjoying it.  

The conflicts that it has with other levels are the fault of those other levels, which are poorly converted imports either from Half-Life 2, or levels that worked fine in L4d1 that are poorly converted by Herbius to "work" in L4d2, often with multiple bugs involved.  Those bugs also break IHM2.  The blame lies with the converter, Herbius, who is unwilling or unable to fix such bugs.  Be aware of which levels you download that are poorly converted by him.