don't want to get into that mac/pc flaming debate, but just for information:
the mac is really great for programming especially with it's free bsd underpinnings, you get the regular apache webserver and php preinstalled,
all major webservices like mySql and so on are available as a nice installer package and it just works
also there is a great programme called "bbEdit" for scripting that works neatly with nearly every language and there is even an actionscript syntax coloring plugin for this app!
the only think i ever wanted to try, which is not available for macos is the mm remoting stuff, which is windows/solaris only, but hey, there is amfphp and it's free