Working good for me. On a 2.8 Quad-Core Intel Xeon.

Kudos to Blizzard for still supporting a 12 year old client!!!

Haha, I can't believe Blizzard is still updating this game. Props to them for doing it. Gotta love those guys. Anyway, here's the official patch notes for 1.13d from the Blizzard forums:

Patch 1.13d - 10/27/2011

New Features

Ignoring players is now saved between sessions of the game. All ignores are now written out to disk (file: 'ignorelist'). This feature can be toggled by issuing the command '/ignorepersist'.
Users can now filter messages based on content by issuing the command '/filtermsg '. To unfilter content issue the command '/unfiltermsg '. (The maximum length of a filter pattern is 128 characters)
Users can now set their home channel by issuing a new Battle.net chat command '/home ' while in the Battle.net chat interface.
Users can return to their home channel at any time by issuing the command '/home' while in the Battle.net chat interface.


Major Bugs

Fixed a known dupe method.
Fixed another issue where players were able to stack auras in an unintended way.


Minor Bugs

Fixed a bug where Mercenaries wouldn't have multiple auras active when they should have.
Fixed an issue where players could create games prefixed with color codes.
Potentially fixed an issue where players would be disconnected when watching the cinematics when in a Battle.net game.
Fixed an issue where the game would crash when running in windowed mode with sound disabled and the game tried to play a cinematic.

Ugh, this update has made things WORSE!

Constant freezes/crashes/unrecoverable errors have made this unplayable. Thank God for Time Machine backups!

Diablo 2 runs fine on Intel Macs in software mode with some minor slowdown. If you need a native OS X installer (older discs don't have it), download it from Blizzard's support site. Hold down option while launching to choose software mode instead of opengl. OR you can run open GL windowed mode just fine. Simply setup the game to run OpenGL and when you get the "bouncing" title image screen after opening cinematics, hit COMMAND-M to go to windowed mode and the graphics will clear up fine. The only downer is that the game is still low resolution by today's standards (max of 800 x 600) and that means windowed mode is TINY on your Macbook with a 13" screen.

I am absolutely pleased that Blizzard is still working on updates for a 5 year old game. What other company would do that? It's akin to a well designed automobile- made to last rather than made to make money right now and forget about keepingit on the road.
Verison 1.11 is blazingly fast using software mode on my 300mhz G3 using OSX 1.1.5. The difference is remarkable. I couldn't even play using OSX before the update. BRAVO!
I did have to install the update using Battlenet however. My computer wouldn't let me unstuff the downloadable versions available here. Anyway, stop complaining about how Blizzard "let you down" and start enjoying the fact that there are still good companies out there who care about their products enough to support it for 5 years!