Here are the list of bugs etc I have experienced with the DLC.

Mothershop Zeta

• Bad frame rates, to the point of it being unplayable. In all areas, especially the engineering core.
  
• When first starting the DLC, the Aliens would probe me, and then they just seem to freeze in place, thus not being able to start the quest(s).
  (Fix: Deleted all save games, and started a new game. Works perfectly now)
  
• VATS freezes, Mothership Zeta is the only place where I encounter VATS issues.

Broken Steel

• Terrible lag issues, especially when there are explosions from Liberty prime.
  
• When starting the main Broken steel quests liberty prime will get stuck, and I cannot proceed to the bridge, due to there being a massive area where if I move there I get stuck. Thus not being able to complete Broken Steel.

Operation Anchorage

• Near the end of the DLC the game really lags, especially after taking down the pulse field.
  
• Some NPC's get stuck
  
• After completing Operation Anchorage, the Outcasts will attack me for no reason.
  
• Terrible lag in the outcast bunker during the "Aiding the Outcasts" quest.

It's a shame that none of these issues are going to be patched. The PS3 needs these patches. Please Bethesda....

I have had no problems with The Pitt and Point lookout however. These DLC's have been mainly lag and bug free.

I have the same problems. I can't complete Broken Steel because the game first lags horribly and then freezes. I tried reinstalling and rebooting but that doesn't help.