If OS X is programmable, and I wanted to get it, what is the best system to go for? Is it upgradeable/tweakable?
Can you post links to some info and impartial reviews?
Mac OS X is fantastic for programmers. You have a full Unix underneath the UI, and Apple's developer tools are free; they come with the OS X retail package and you can download them from the web. The Cocoa API is the best I've seen on any system. Apple is definitely encouraging third party developers much more than they have in the past.