Software that won't work on Intel Macs:
- Classic Environment, and subsequently any Mac OS 9 or earlier applications
- Screensavers written for the PowerPC
- System Preference add-ons
- Applications which specifically require the PowerPC G5
- Kernel extensions
- Java applications with JNI (PowerPC) libraries
Any other PPC software should run fine with Rosetta. Any Universal Binaries (like the iLife apps) will run natively.
URL="http://wiki.mozilla.org/Mac:Intel"]Firefox has already released OSX Intel builds of their three big products[/URL].
For Apple's pro apps they're charging a nominal fee to cover packaging and shipping. I'd expect many companies to follow their lead.