First, just to be clear: if you have ever run D&D campaigns in the past, do not get this adventure. Contrary to the marketing, it is purely for first time DMs.
And while I'm contradicting the marketing... this adventure has nothing to do with The Shattered Gates of Slaughtergarde. Do not buy Scourge of the Howling Horde if you're looking for an introduction to The Shattered Gates of Slaughtergarde. I fell for this, and was extremely annoyed.
For experienced gamers, this adventure has little to offer. Aside from the simplistic concepts that even a novice DM could have created, there are significant gaps in logic that really ruin this for me. The final encounter is a great example, as was previously commented on. Another example is the hobgoblins wielding long swords and wearing studded leather armor, while in a chest (that only they have the key to) are a magical long sword and magical studded leather armor.
They may be hobgoblins, but they are not that stupid.
There are additional issues, I am avoiding any spoilers in case players might take advantage of them.