[Jon Francis (OP)]

Does gravity act on anti matter in the same way as it does to matter?

[JP]

I think most physicists believe the answer is yes.  We haven't actually been able to test this with single particles, however, since gravity is very weak compared to the other forces.  There's not really a theoretical reason to think that antimatter would behave differently from matter. 

If gravity repelled antimatter, there would be another oddity--photons are attracted by gravity, but they could be seen as their own antiparticle.  (Or, if you don't like that, an electron and a positron can collide to create two photons.  If the photons are both attracted by gravity, along with the electron, it would be odd if the positron was repelled.)