stwert: i thought you said you use a seven button mouse and i was going to ask if i could have it :p
effortless buttons makes for faster productivity...

yeah, i have my keyboard and mouse setup for right handedness
thumb on alt/spacebar key, little finger on shift, and the others on q,w,e, r, g, z, x, c, v, b (one reason why i like the setup in maya over xsi, since xsi has the w,e,r functions at the bottom of the keyboard and the fingers squash up and i'm more likely to use the manipulation tools rather than the tools xsi has assigned to the keys up top)
easy access to ctrl+shift+d, ctrl+d, and alt, shift and ctrl

pros of the default setup? you have your right hand on the mouse and left hand on the keyboard, and it's on the keys that you're probably going to use the most.
might take you a while to get coordinated but it wouldn't be too too long before you get used to it.
everything you need is quick access other than delete and insert/home. enter button is right next to your mouse as well... even if you're using those stupid new mac keyboards

cons of the default setup? using a mouse and keyboard is probably a con :p

every software company feels the need to remap the functions of each key to a different thing. i sometimes use alt+mmb in photoshop by mistake, or soemtimes i hold down the right mouse button in other apps...
you get used to using a 3 button mouse... dont know how you live without at least 5 buttons... although i suppose that magic mouse probably works fine... middle mouse button on that doesn't always work though, dont know if it actually works in maya