I purchased this for the fit bit blaze. I noticed the first few times it really wasn't able to tighten enough to my wrist in order to provide an accurate heartbeat reading. I would compare it to exercise machines at the gym as a baseline and other monitors I have.
I found the leather to feel more natural, but it honesty felt like cheap leather. The Stainless Steel casing was painted such that it looks more plastic than anything.
For the price of the band to customize the watch, I felt there was no value. The Apple watch has a variety of options and while the watch has a high start point, bands can be purchased aftermarket by homemade sellers, retail, etc for around $30 for a much better leather and style.
I just think at the price point, its overpaying for a simplified device. I rather where my old analog watches that are timeless and reliable and made of much better quality leather. $100 is overpriced for this band. Its honestly worth $20-$30 and will probably be there in a year.
I give it 2 stars for functionality. Minus 1 from 5 for quality, minus 2 from 5 for price.