Waiiiit, how did you get the Alpha 6.7 update? Steam didn't do an update for me. Unless it's the 'beta version' setting.
Anyways, while the new collisions look great, I was kind of expecting, I dunno, it to be more cataclysmic? Although the pluto hitting mars one looked more like it was absorbing it than a collision, great to see that the radius changes with mass.