I’m under NDA so I can’t talk about the details, but I must say that I am really excited about the new APIs (and improvements to existing APIs) that Apple will be offering to developers in Leopard.
Some of the stuff is annoyingly good, in fact; annoying because in many cases I spent days or weeks implementing stuff myself which Apple will be offering "for free" in Leopard.
The rest is just plain good. Rather than hold back as I have in the past I think I’ll be upping the minimum requirements for most (if not all) of my apps. I will continue to support the older versions of Mac OS X, but only for bug fixes; most of the new feature work will go into the Leopard-only versions.
As an example, let’s say that a given app is at version 2.2 in its current form. I will probably do a 2.5 release that will be Leopard-only. From that point on all the new feature work will go into 2.5 and up (2.6, 2.7 etc) and only bug fixes will appear in the 2.2 series (2.2.1, 2.2.2 etc). The older series will continue to be available for download alongside the newer versions.
It’s quite exciting really… considering that Synergy is still a Jaguar-and-up application, Install is also, and all the others are Panther-and-up. Really looking forward to seeing what can be done when future releases of these apps start requiring Leopard.