Pros:

-Finally a challenge on expert, making the official campaigns fun to play again.
-It is very balanced even tough I imagine the run of the mill player having problems reaching the saferooms and would say otherwise.
-Tank music is awesome, hums along every time.
-Alterations in the finale eliminates often used strategies.
-Spawning tanks behind the player forcing them to flank backwards or run for dear life is brilliant.

Cons:

-At times there are minor bugs with the spawning of bosses including double spawn of witches for the entire level and nav issues that could be exploited.
-Spawning bosses in plain sight is not nice to the player, but these spots are avoided by trial and error.
-Electrified buttons can be avoided but there is no hint of how to do this.

Conclusion:

This bundle made the official campaigns worth playing again, which I for one haven't touched in a couple of years.
These campaigns are not suitable for beginners by any means, but if you have a friend/friends that always complete campaigns with ease on expert and know every trick in the L4D book, this is an awesome addition to the addon campaigns!
I really would love to see the creator(s) release similar HEM versions of The Sacrifice and Crash Course.
10/10 addon in my book.