Minecraft gets EXTREMELY laggy after it has finished loading regardless of render distance or in fact any setting. This even happens on tiny render distance. I have had lag before but not to this extent. I don't know what's causing this but I really hope it gets fixed otherwise Minecraft would be unplayable.
Where lag usually doesn't happen:
Superflat worlds
Basic Terrain
The End
PS. Optifine/updating LWJGL doesn't make a difference whatsoever, in fact it actually slows it down even more.
Comments

I can't do that, I installed the new Java 7 for Mac but Minecraft doesn't seem to use it. Edit: When I try using the MinecraftLauncher.jar file in the actual Minecraft Launcher package, it DOES use java 1.7 but crashes with a LWJGL exception.
Your Java is still outdated. While you are using 6u35, 6u37 is available.
Download here from Apple's official servers:
https://support.apple.com/kb/DL1572
Java 7 is not yet properly working on OS X.
Thank you Martin for reminding me to update. The update has made a slight difference in performance but I'd like to see the problem solved completely. Or an OS X version of OptiFine.
No the lag hasn't been fixed, even after the java update. The lag is getting substantially worse too. Survival is impossible without death.
This is NOT resolved. It is a very common problem and should be given further attention! It got even worse in 1.4.2
There is a forum for this on the minecraft website.http://www.minecraftforum.net/topic/1403906-131-fps-issues
I was quite annoyed at my post getting marked invalid. I feel like all mac users are getting ignored and 'oh thats just your problem' said to them. And yes if someone does come along I know this comment might not be suitable for this site and should be directed to the forums. 😞

It's just that there is not enough information to support that this issue is specifically a bug relating to the minecraft client, as opposed a hardware issue, or operating system issue. In order for it to be solved here, it would mean that the developers would have direct access to your computer, because frankly there just isn't enough information.
Minecraft should run much more efficiently. My computer runs perfectly on everything else but Minecraft. I see others with awesome specs but they still get terrible lag. You'll just have to experience it for yourself to see how frustrating it is.
I have a good computer and, before I get the lastest launcher and the 1.6.1 patch, the game was really smooth. However, after getting the new launcher and the new patch, I get 8 FPS all the time.
Exactly the same for me Registeel.
I am suffering similar problems. Game used to be smooth but is now jerky and landscapes/ backgrounds are incomplete.
I have happily played on iPad for 3 years so it is def the game not the equipment.

@unknown, this report is 4 years old, and is for the PC edition. It is recommended you look at the MCPE section of the bug tracker for your issue on mobile.
You should try updating your java. I found it to give a performance boost.