I bought this when it was released. All the games have slowdowns as far as I'm aware, and the worst offender is Runner, where the slowdown is present throughout the entire game, 3D or not (turning off 3D improves it but it is still very noticeable). In other games it happens sometimes when there are a lot of particles on the screen, 3D or not, but with 3D on it is more frequent. It boggles my mind that they released this collection without optimizing it. It doesn't seem that hard to me to make a game that looks like this run properly, and my respect for Gaijin Games has fallen a great deal since I purchased the game. Saga disappointed me too much. It feels like a major waste of potential and a cash-in. I'm sorry for being so negative, because they are good games, but a developer that releases a game for a specific platform and cannot make it run properly is one of my biggest turn-offs in gaming, and it is becoming far too prevalent between this, Virtue's Last Reward (which I could forgive because it wasn't an action game) and Code of Princess (which I find nearly unplayable).
Definitely worth $15 if you are into that type of game.