This is both one of my favorite modules to run and the only module in which I have ever had a party wipe.

I'd say the biggest concerns for this module are resource consumption (large numbers of small fights in the mines themselves) and the danger of the optional (but likely) bulette encounter. A melee-focused party will have a particularly tough time with the bulettes (that's where I wiped a party).

Additionally, the size of the mines section themselves can cause the module to exceed time fairly easily. Consider moving the "functional" guardians to wherever the party goes first in the mines (i.e., the map is out of date) so that the party makes full use of their ability to reduce the number of available encounters.