Just a quick tip for any other “traditional notes client developers”. With traditional Notes applications it has been very very rare that an upgrade has caused problems with functionality, I have only ever seen it a couple of times over thousands of applications.
We upgraded to 8.5.2 yesterday and both of our Xpages applications currently under development stopped working. In both cases 8.5.2 was fussier than 8.5.1 about tolerating some dubious SSJS code.
as an example this code worked on 8.5.1
var Statusnumber : integer = Statustext
whereas in 8.5.2 it required the more correct
var Statusnumber : integer = parseInt(Statustext)
While this may indeed be the correct thing to happen the combination of steep learning curve, significant server changes in a point release and a complacency built up over years as a Notes client developer may also affect a few other people so heads up.