"First, let's get the frame-rate thing out of the way. Yes, Half-Life 2 has its slowdown troubles, and occasionally they are ugly. Not necessarily "throw your Sixaxis against the wall" bad, but certainly noticeable. Fortunately, these laggy moments are relatively few and far between; for the most part, the game runs just fine on the PS3. But in these moments--for example, when speeding through the sewers of City 17 on the hoverboat as you're being tracked down by the helicopter--the chop can really pick up. Although you might expect some frame-rate issues during a high-speed chase scene, there are moments of relative calm that have frame drops as well, such as at the way station directly after you have blown the battle copter out of the sky. As we crossed the structure so we could open the gate to give our airboat a chance to jump through, the game's frame rate would slow down here and there, despite not much happening onscreen.
After that section, frame rate in the game seemed mostly solid up to Ravenholm, which is as far as we made it in our play-testing. We didn't spend a ton of time in either Episode One or Two, but we did notice some frame-rate issues in both--again, nothing game-killing, but it's certainly something to be aware of. One other thing to keep in mind across all facets of the Half-Life 2 suite (including Episodes One and Two, as well as Portal): You can quicksave your game on the fly at any point by pressing and holding down the start button. You can continue to play the game when quicksaving, but the frame rate sometimes takes a severe hit while doing so, especially if there's a lot happening onscreen."