i switched 2 months ago and love it, never had touched an apple before
took a few days to get used to some keypad shortcut differences and the tricks you can do with the trackpad gestures. those are essential.
confused for a few days about the delete button, which is more like a backspace than the delete you are used to. ... fn+delete was a great find for me
for the first week i had mine i didnt like the mouse since i was so used to the 2 button PC mouse... then i realized you could go into your mouse settings and set the right side for "seconday" and then you can right click on things
discover the spotlight (magnifying glass in upper right corner) that thing is a godsend!
and yeah, adium rocks
i had a thread a while back with similar questions, and had some good response on various programs you may want to check out
http://www.gfy.com/showthread.php?t=...ighlight=apple