With the release of their two Spring 2004 devices, PalmOne has also updated their SDK to version 3.0 (although the readme file says 2.5). This new SDK release includes more examples, details on their new CameraLib 2.0, a description of the Codec Plugin Manager on the Zire 72, and all the goodies that were in last year's SDK 2 release.
The new simulators don't have much documentation included. The only text file I saw in the archives was the end-user license. After checking with PalmOne developer support, I confirmed that they use the Alt-Up/Down/Left/Right and Alt-Enter keys for simulating the 5-way navigator control, so if you've been working with the Treo 600 simulators, you'll need to adjust your fingers for the different scheme.
You can get the new tools at the PalmOne PluggedIn developer site: http://pluggedin.palmone.com/.
By the way, a little bird tells me that PalmOne will be expanding their on-site developer forums to include areas devoted to their Zire and Tungsten devices. They currently have several nice forums for Treo developers; it will be good to have special support forums for developing for their PDA devices too.