Premier IBM Business Partner Intec has a fantastic updated whitepaper entitled "Maximising the Benefits of XPages in 8.5.2:

Almost a year ago I wrote a whitepaper called "Maximising the Benefits of Lotus Domino 8.5.x with XPages". This was an open discussion of the pros and cons of XPages, based on Domino 8.5.1. I have updated the whitepaper to take into account the significant enhancements in XPages in 8.5.2 and a year's more experience of developing applications in XPages.

XPages is still, in my mind, a game-changer for Domino, providing in a RAD environment capabilities that have not been available before without significant effort, if at all. Yes, RAD has a reputation of quick and dirty or prototype, and XPages can be that if you want it. But It also provides the framework for building a sophisticated application and makes UI design more important than ever before.

Maximising the Benefits of XPages in 8.5.2 on the Intec blog >