You use Directory Utility  to join a Mac to an Open Directory in Leopard. It’s convenient because you only need to use one application. When I tried to add a new iMac running Snow Leopard to our Open Directory, I found that there is no Directory Utility in /Applications/Utilities . The utility is hidden in /System/Library/CoreServices , and you cannot use it to join the computer to the Open Directory. Therefore, it’s not very useful.

The function of joining the computer to OD has been integrated into the System Preferences. To do it, follow these steps:

1. Click on the Apple icon on the menu and select System Preferences.
2. Click on Accounts -> Login Options.
3. Click on the Join button to join the computer to a Network Account Server.
   

You can open the Directory Utility from the poped up dialog. However, the ability to mount NFS shares is also stripped out from the Directory Utility. To mount NFS shares, use Disk Utility instead.

1. Invoke Disk Utility.
2. Click on File -> NFS Mounts.
   
3. Add the shares.

When you run a Java application on Snow Leopard, the 64-bit Java is used by default. This might be problematic when you run some older applications. We ran to this problem earlier when a user tried to activate his Matlab license. The message he got is

There was an unexpected exception: Can’t load library: / Applications/ MATLAB_R2009aSV.app/ / bin/ maci64/ libactivation.jnilib See the log file (/ var/ folders/ Mp/ Mp0PQFo9GbKznsjhgBiZf++++TI/ -Tmp-/ TMW_svact_christophergiuliano.log) for more details.

The solution is to set the 32-bit Java as default. Here are the steps:

1. Invoke Java Preferences in Applications -> Utilities.
   
2. Click on the entry of Java SE 6  32-bit and drag it before Java SE 6  64-bit in the Java Applications section.
   
3. Close Java Preferences. The 32-bit Java will be used next time you run a Java application.

Snow Leopard is out today. If you are considering upgrading to it, the first thing you need to know is that all the software for PowerPC are not working any more. There are some other Intel based software which are not compatible. For a complete list of those incompatible software, please visit this link.

http://support.apple.com/kb/HT3258

[Update] There is an unofficial Wiki page about application compatibility under Snow Leopard. This list is much more comprehensive than the official page.

http://snowleopard.wikidot.com/

Snow Leopard is due out in a few days. If you have bought a new Mac without Snow Leopard after June 8, 2009, you might be qualified to get the upgrade for $9.95 plus tax. For detailed information, please visit this link.