I have a few tips you can try that have worked for me to fix the problems on the PS3, or improve preformance. Hopefully these tips work for you!
(Info about my system: 160GB PS3, Black, Not Slim, and has 104GB of memory left.)
(Info about my saved game file: 13MB of saved memory, Level 46, and 135 hours of gameplay.)
Tip number one: Rebuild your PS3 database every week. (This REALLY works wonders for me!)
Tip number two: Delete all game and saved data from other games (Not Skyrim) that you don't use/play anymore.
Tip number three: Do not fast travel, walk everywhere. (If you fast travel too much it'll start lagging horribly. I tested this out by fast traveling 7+ times in a row and the game continued to lag horribly. If you lag horribly due to fast travel, save your game then go rebuild your PS3 database. That'll fix the problem.)
Tip number four: Forget horses, walk. (Mounted combat doesn't fascinate me either way and they always get in the way of fighting anyways.)
Tip number five: Turn off all auto-saves, just save manually. But don't save-bloat! Like save every 30mins or so.
Tip number six: Pick up weapons and items off the ground that are stray and sell/store them indoors. This will help greatly!
Tip number seven: Don't use whirlwind shout often to get around, just walk a normal pace and admire the beauty! It allows the game to load the world properly.
Tip number eight: Don't try and expose glitches and bugs that'll benefit your gameplay such as the book from Mora you receive when playing the main quest. (We all the that super level up glitch) It breaks your game.
AND FINALLY... If none of these have worked for you after a MONTH time. I would wipe out your PS3 completely and start all over. This is a LAST RESORT. Only do this if nothing works or improves over time.
I hope you all find these tips helpful!

And how pray-tell do we do this?

Tip number one: Rebuild your PS3 database every week.