Can 10.4 apps be built with Obj-C 2.0?

FROM : Todd Blanchard
DATE : Mon Nov 05 23:36:01 2007

I haven't installed Leopard because I'm in the middle of upgrading an 
app with a lot of 10.4 users and it has to run there.  So I just have 
a quick question - are any of the goodies useful for building 10.4 
compatible apps or should I stay where I am for awhile?