Available in LIB version 2015.2.914, it will be also available in the 2015 Q3.

If you apply a number format to a Count value in the RadPivotGrid, then it is ignored. The reason given is that count is always an integer, so it shouldn't need formatting. However, I'd like to be able to apply group separators. It's much easier to read 100,000,000 than 100000000. 

Available in LIB version 2016.2.606, it will be also available in the 2016 R2 SP1 release.

Currently it is only possible to either show all or hide all subtotals.

The DistinctValuesLimit property is available in our R1 2018 Release.

It happens when you change the distinct values selection several times. The PivotGrid disappears after the exception is thrown.
I managed to reproduce it in the demo by repeating this action around ten times.

Currently the header of that column says "Grand Total" instead of the aggregate name.

RadPivotGrid is loading all data from OLAP Cube. It should be able to use on demand (lazy loading) pattern, so when a group is expanded, a new query is sent and only required data is taken from the server.