Pros:

Great textures.
Great model ( even has drum style clip ).
Authentic "Chicago Typewriter" firing sound.
Breath of fresh air for people like me that have been wanting this gun in L4D2 ( I mean come on its a tommy gun vs zombies how cool is that?! )

Cons:

This isnt really a con but worth mentioning. Some people ( such as myself ) have to manually install the vpk file in the l4d2 add ons folder, even though when you double click it, it says its installed. 

Go to Extras and check add ons to make sure the mod and sound are listed.

Conclusion:

With great modeling, skin / textures and an easy to install this gun gets a high rating!