All of the answers have 180 degree rotational symmetry!

For the acrosses, the top left corner begins with DAP. The bottom right ends with PAD. Then OGRE/ERGO, REED/DEER, and so on.

For the downs, it's DORA/AROD, AGES/SEGA, PRET/TERP.

And right in the middle, two palindromes STETS and RACECAR.

Every single letter in the top left has a matching letter in the bottom right. It's an insane feat of puzzle construction.