Congratulations on beta. At least no immediate crashes or anomalies under Win 10 build 14393.222. Just tested a couple of existing files and messed around with them. Everything normal, and saved files open nicely with 5.2a without a problem.

..navigation in the 3D view is slower with Java3D 1.6 than with Java3D 1.5.2...

Possibly, but hard to say - nothing very obvious (but with relatively small files).

Do tell if there are specific procedures you would like tested.

ok