After playing for around 30-45 minutes, I really couldn't see anything wrong from the viewpoint of a casual gamer. I open the AvP game, select multiplayer, and allow the list to be populated with all of my different choices. Of the 4 games I connected to, I only noticed a slight lag on 1, and that was mainly attributed to the high pings that everyone had. But even then, it was barely noticeable.
Basically, Galaxy functions almost seamlessly.
But I did notice that when I select the multiplayer option from the main menu, my CPU usage all of a sudden reached 100%, and it's only like that when I'm waiting for a game. When I'm in an actual multiplayer game, the usage is what you would expect from a game. This could be an issue with the actual AvP game itself, but even then it would be nice to not have my laptop fan kick in for such a short period of waiting. If that one problem could be fixed, then I probably wouldn't be able to tell you that anything was wrong.
Aside from that, the game functioned as I would expect from AvP Classic 2000, and I can't really say anything against it even if I wanted to, considering how respectably it performed.
I will definitely be back to play some more, and if all goes smoothly like it has been or something changes, then an update from me won't be necessary, considering how the game and Galaxy component have practically proven how GOG is definitely on to something in the multiplayer aspect of the games they are offering.