Indeed, the word "Peal" on the E-Ink product page
does not have ™ next to it, unlike Vizplex™.
Some people on the-ebook.org forum have claimed that Pearl screens are just the top tier of the Vizplex screens, i.e. they don't have a new production process or anything, but just more stringent QA process. There might be some truth in this, but I
think it's a combination of 1) better (blacker) ink particles, 2) new/optimized waveforms and 3) the new ISIS controller that can make use of those waveforms.