Looking at the pricing per month and some key functionalities, we can see that PPU is placed between the Pro and Premium Capacity.
In our opinion, the most important features of the PPU license are the possibility to use deployment pipelines (application lifecycle management), take advantage of more performant dataflows, and the possibility to use paginated reports (send printable reports and pdfs to stakeholders).
In the past, when a company with 10 Power BI Pro users needed premium features, it faced a massive monthly price increase from € 84 to € 4.212,30. Now with PPU, the monthly license fee increased to € 169 instead of € 84, which is more acceptable.
Keep in mind that not every type of license (including PPU) can collaborate with other types of licenses. A pro user will not be able to see the reports of a PPU user. However, a PPU user will see the data of a Pro user.