Thanks for everybody's input.
I ordered all the parts and put it together a couple of weekends ago. I have tested it twice and both times it performed very well. It will overshoot by 5-10 degrees then cool down to the target temp before staying at the target +-1degree.
I have a couple of comments:
1) The box/case that is specified above is not deep enough and you have to cut out the lid to fit the PID. I should have checked this as I noticed that a few people did this in their photos. Really easy and cheap to fix (when I get around to it)
2) There was some talk of needing a flap to block the air going in while the fan is not running. I don't need this on my set-up on a Kamado Joe.
3) Don't think you can get all the parts for $50 anymore, however they are not much more.
Happy to answer any questions that anybody attempting to build this might have.