I searched recent Reddit /r/Skyrim posts for "PS3 lag" and it seems that people playing Skyrim on PS3 still experience the issue you mention.
Explanation from Reddit - /r/Skyrim post, "PS3 Skyrim bug, needs some publicity":
There exists a bug in the PS3 version of Skyrim which, when your save file exceeds a certain size +6mb or so and you have been playing for about an hour, you'll experience a certain amount of lag, over time becoming the unplayable sort.
Currently the only remedy is to restart your game, resetting the timer
until something builds up the lag. The real issue for now, is the
certainty behind the fix. Unfortunately, this bug actually existed in
Fallout 3 & New Vegas, though was less prevalent because it took much
longer for you to achieve a save file large enough to cause a problem,
however the bugs still exist in those games to this day and never saw
a fix.
From a Kotaku article, "Do Not Let Skyrim Overflow Your PS3":
After Skyrim gamesave files surpass 5MB in the PS3 version, many claim to experience lag and stability issues. "Such as framerate
issues, poor rendering, shoddy loading and non interactions fro
finishing quests/cutting wood etc," wrote gamer PurpleHaze on the
game's official forums.
"I can't finish ANY quest and i can't buy from ANY trader/npc and i
can only talk to them after some laggy button pressing," continued
PurpleHaze. So my gamesave is now 6mb (how i don't know since i
couldn't buy/sell/talk or complete quests) and the LAG and framerate
issue is so bad at this point, the game isn't worh restarting."
PurpleHaze, whose issues started after hitting 5.3MB, isn't alone,
with other players experiencing similar slowdown once their save files
pass the neighborhood of 5MB~6MB (some are reporting problems after
reaching 10MB).
"My file size is growing constantly, and fast," wrote player AMG
on the game's forums. "It's already well over 3mb in size and I've
only played for 3hrs."
The current fix is to restart the system, which makes Skyrim playable.
However, after an hour or two of play, the game once again apparently
becomes laggy.
This issue does not seem to affect the Xbox 360 version nor the PC
version. Even gamers with plenty of available PS3 hard drive space are
having problems.
"It does not take long for the save file to exceed 6MB, roughly 16
hours for me, so playing the game in any sort of depth will become
very troublesome," wrote Kotaku reader Toby.
In the above gallery, there is game footage of what looks like people
experiencing these issues (note that they might be experiencing
unrelated glitches, too). Players are calling the PS3 version
"broken".
Also, see Gamesave size limit, lag and no interaction of NPCs | Bethesda - Skyrim forums.
Possible fixes (from Bethesda - Skyrim - PS3 forum post, "Skyrim Performance Tips" by Gstaff, a Community Manager):
Always update to the latest patch. We continually improve performance
with each update.
If you start experience framerate and performance issues, save your
game. Restart your Playstation 3 and reload the save. If the
performance issues persist, here are other things to try.
Turn off auto saves. This can cause temporary stuttering since the PS3
saves these files in the background This is most noticeable with large
saves when fast traveling to a new area or entering a new area that
auto saves.
Waiting for time to pass. Many things are running in the world
depending on what quests you've done or places you have visited. Using
Wait or Rest options, passing time will clear up some of these. It
depends how long you wait, it may take up to 30 days for some items.
Saving, resetting, and loading after this will have the largest
effect.
Save your game and restart your Playstation 3 during long play
sessions (6 hours or more).
If your game is freezing when entering water, make sure you’ve updated
to the latest patch.
If you’ve updated to the latest patch and you encounter strange
behavior immediately following application of the patch including
queued messages appearing on the screen, just wait and let this
process run its course. This is a temporary effect of certain Skyrim
scripts correcting themselves after the update. Once this process is
complete, make a new save and restart your Playstation 3.
Clear space on your hard drive. Clearing at least 2 or more GB of
space for best results. Skyrim makes heavy use of the hard drive, and
freeing up space on here seems to help many people. Hard drive speeds
also differ in PS3 models. Some users have reported increase
performance by upgrading their drives.
The PS3’s Safe Mode* feature includes options that can help with
memory fragmentation.
Restore File System. Attempts to repair all areas on the hard disk
drive where files can be saved. Corrupted data may be erased, which
can help performance.
If you choose not to enter Safe Mode, you can manually delete
corrupted saves within the XMB menu. Go to Games>Saved Game Utility.
Within the menu, delete any corrupted save files. These files can be
created from Skyrim and other games when a game doesn’t save properly
(shutting down the console before an autosave completes, etc).
Rebuild Database. Will help with memory fragmentation on the PS3 HDD.
Note: Using Rebuild Database will erase messages, playlists, changes
made on [Information] screens, trimming information for pictures in
[Photo], video thumbnails, video playback history and video resume
information. The content that is erased will not be recoverable.
*Sony does not recommend using the options in Safe Mode unless you are experiencing issues with the PlayStation 3. Some of these options
could result in loss of data.
