Many Mac enthusiasts may already be taking inventory of applications on their system in preparation for their upgrade to Snow Leopard. One question that will likely dominate the support forums and social media networks is "will my application work on Snow Leopard?"
The simple truth is, for the most part yes. While Apple is taking great strides toward a 64-bit future, they're not about to abandon a 32-bit universe of apps. OSX 10.6 will have great support for your existing applications, however your plug-in experience may be a bit different.
Apple has re-written most of the core applications in 64-bit. This includes everything from the Safari to Address Book. Over the course of time, many applications have had third party plug-ins developed. Plug-ins, more than applications, will suffer from this change.
Safari Plug-ins will need to be re-written for 64-bit. While running Safari 4.x in 64-bit mode with 32-bit plug-ins installed won't prevent it from launching, you will need to force it to run in 32-bit mode for your plug-ins to work.
This is accomplished using the "Get Info" command (CMD+I) and checking a new box titled "Open in 32-bit Mode." Safari does ship with a 64-bit version of Flash, if you do run in 64-bit mode, the millions of flash-enabled websites out there will still work.
Even the System Preferences application has been re-written. Having preference plug-ins such as Growl and MacFuse will not prevent these plug-ins from working, however it will present a dialog stating System Prefrences must quit and reopen. The tag "(32-bit)" will follow the title of the preferences panel. System Prefrences will remain in 32-bit mode until relaunched. This remains the case even if you click on a 64-bit enabled preferences option.
Itunes and QuickLook plug-ins will all work fine as both are still 32-bit native applications. With the large number of plug-ins written for iTunes, this may have been one of the deciding factors why iTunes was passed over for a 64-bit upgrade.
So while you are making plans for your upgrade to Apple's new OS X 10.6 Snow Leopard, be sure to take into consideration any plug-ins you may have installed as well.