Pros:

Awesomely vast backdrop
Prompts to help guide the survivors on where to go and what to do at different stages of the battle
Inclusion of LOTR music
Nicely constructed castle

Cons:

Ending although pleasant is a little anticlimatic; could include something more special to see or do rather than simply be left stranded
Gandalf appears to be nothing more than a statue
Abundance of molotovs inside the castle makes it a little too easy to fend off the horde

Conclusion:

An epic map for survival mode with the potential to be that little bit more epic.