Hi Ryan,
I remember when the D3s came out. Lots of people saying it wasn't much of an upgrade from the D3.
We soon found out that is was.
Like most things in life, everyones an expert. Some even without touching the product that they claim to be an expert in.
It hasn't cost me a huge amount to upgrade. My attitude is that after listening to the talks by Nikon at Focus and believing that Nikon aren't likely to take a step backwards when producing their top model dslr, it wasn't much of a brainer for me to change.
I like the improvements with the focussing system. To be able to bolt a 2 x converter on my 300mm or 200-400mm and have auto focus swung it for me.
have a look at this review by Richard Peters:
http://www.richardpeters.co.uk/blog/2012/01/31/my-hands-on-pre-production-review-of-the-nikon-d4/
Kev.