Colemak is supposed to perform slightly better then Dvorak as a layout, and be easier to learn for a qwerty typist.
http://colemak.com/ http://en.wikipedia.org/wiki/Keyboard_layout#Colemak
Second vote for Colemak here! I spent the first two of my high school years in Japan essentially being homeschooled. I had developed shoulder pain and a ganglion cyst in my wrist due to lots of typing and playing tennis, so I took the opportunity to try both Dvorak and Colemak.
I used to average 110 wpm on Qwerty. I started at 30 wpm Colemak and reached 80 in three months. After fourish years, I'm back at 110 wpm, with no more cyst or shoulder pain.
I tried Dvorak for a week but disliked that 1) it emphasizes hand alternation (as opposed to Colemak's emphasis on finger mashes) and 2) it was so difficult to type "ls -l".
I haven't actually tried an alternate keyboard layout yet so I can't vouch for it, but Colemak seems to have the edge on Dvorak.
I also do the ls -l thing all the time and finally succumbed to just uncommenting the relevant alias in my .bash_rc. 'll' just makes it easier; I don't know why I resisted enabling the alias...
also, i love my apple keyboard and was worried about using something else, as i use them on all my machines, including linux boxes. did some research and found this:
http://www.kbcovers.com/servlet/Detail?no=154
ordered three. thanks mattmight.