To see immediately an example of Bmesh ngon support, click on Add -> Mesh - Cylinder
And look at the top and bottom faces.
But play a lot with the knife ( key shortcut being K ) , it’s simply fantastic and extremely usefull, for this knife alone it was worth making the editmode core being Bmesh.
By the way, i was looking at the “testbuild” version , it’s apparently revision 45364
I must say it’s already outdated if i look on the buildbot, that for my system has currently revision 45412 and has some more bug fixed than the “testbuild”.
So if you want to contribute in reporting bugs, it may be better to use a Blender from the buildbot so you don’t report bugs that may in fact already be fixed.