Update:
My Series 4 / 44mm Space Black came in on Monday. I took a few comparison pictures with my Series 2 / 42mm Space Black and my new Series 4 before I sell the Series 2.
I tested with the sport strap that came with my Series 2 watch and my Nomad strap that I have been using since I bought the Series 2.
Series 2 Sport Strap
Series 4 Sport Strap
Series 2 w/ Nomad Strap
Series 4 w/ Nomad Strap
I agree with the original articles, the previous straps perfectly fit with the Series 4 watch.
I am very impressed with Apple's Space Black finish and the Sapphire face, my Series 2 watch still looks brand new.
Notes to mention:
The Series 2 Stainless watch came with a square storage case but the Series 4 Stainless watch did not come with any sort of storage case. It is more expensive with the Cell & EKG features without the case. Oh well, I never used the storage case for my Series 2 anyway.