Pros:

Extremely Detailed
Well thought out
Did not experience any nav problems!
good mix of outdoor and indoor level design
Fresh new way to end a campaign
Never experienced color changes within source before

Cons:

Ending "movie thing" the background looked horribly pixilated, but guessing you had to use a camera on a brush background or something of the sort somewhere else within the level.
The finale in my opinion could have used infected coming from more than one angle.

Conclusion:

Wonderful campaign, you can tell the massive amount of time and love that Kev has put into this, very much look forward to the next thing to pop out of his head.