With over 300 new features in the last update to Mac OS X Leopard, you'd think Apple would take some time to relax a bit, but already they're testing the next update. Testing of Mac OS X 10.5.3 started this week, according to AppleInsider.

Build 9D10 has been made available on to the developer community as of last Thursday. Over 75 bug fixes and code corrections in the system have already been reported. Some of the components that have been reported to be in need of evaluation are:

• AddressBook
• AppleScript
• Audio
• Back To My Mac
• CoreAnimation (critical memory leak)
  
• Dashboard
• Dock
• DVD Player
• Finder
• Graphics
• iCal (critical memory leak)
• Installer App
  
• Mail
• Portable Home Directories
• Printing
• Rosetta
• Spaces
• Spotlight indexing
  
• Time Machine
• VoiceOver

This isn't official yet, but Mac OS X 10.5.3 is presumed to be released this April, or May. We'll keep you posted on updates.