Just a quick headsup for those mac users who are not particularly excited about upgrading their OS:

Boatloads of Leopard-only developer environment improvements will likely result in many applications releasing new versions that will no longer work in Tiger (10.4). If you’d like to keep your apps up to date, you’ll have to upgrade to Leopard.

Specifically:

• Objective C 2.0 has been released and it looks like a number of important improvements, such as automatic garbage collection, won’t work under Tiger.

• Core Animation makes it easy to add any number of shiny gimmicks to your app. Core Animation only works on Leopard though.

EDIT: Also check out Matt Gemmell’s partial list of 43 leopard-only development features - use any of those and your application becomes Leopard only.

Personally I wasn’t planning on switching until a suitable version of java 6 is released for OS X Leopard, but possibly I’ll be forced into switching sooner than I planned.

(Of course, Cristiano already switched - that’s his personal copy of Leopard above. He’ll write about his experiences installing Leopard soon.)