Adium http://www.adiumx.com/ is by far the best messenger for mac.
Remote itunes? Why not just move all the music to your new mac.
Drap on the bottom right the window size. There usually isn't any need for the window to be full screen and you will get used to that.
Yeah, adium's the best. Best coding program I ever used: Coda. It's built for macs but it costs 80 bucks. Oh, and if you figure out how to right click with the touchpad, let me know.