I've always loved the Enemy Within from WFRP 1st edition and basically classify it as one of the top 3 campaigns of all time. The intrigue and role playing that it brings is amazing and I was worried when purchasing this product.
Needless to say, I was very pleased. As always the components from Fantasy Flight are durable and all accounted for. The book was also quite hefty coming in around 190 pages. Considering There isn't really any messing around in the book, 190 pages is a lot of information. The quality of the pages, binding, and organization was also great and I don't see myself having to rebind and cover the book like many other companies role playing products, Steve Jackson Games have the worst binding!
The way the campaign flows is very smooth and I like how the option to use Hero's Call material is open if you choose to. I also love how they do the "bad guy" ;) No spoilers!
The only negative thing I can bring are that it's not a full reboot of the original which I was hoping for as the original was a ton of products 5 in total with 2 other option 1/2 products you could add in if you wanted to. Overall though, I am still satisfied with my purchase. But at the same time, if this was a reboot of the original I'd probably be very disappointed as I already have them! Overall, it has the same feel as there is an enemy within, but the story is completely different and pulled off very well.
Comparing this to other campaigns, I honestly would have a hard time doing it. It's basically a long adventure (30-40 gaming sessions depending on what you do), not a full campaign setting that introduces new things. But as a whole, I would throw this next to Ptolus and say that I'm just as satisfied with this purchase as that. If you're not familiar with Ptolus, you're missing out! In terms of an adventure on such a grand scale, I can't really think of any that are as truly epic as these.
If you want something to spice up your game, use this and you'll have enough for a year!