Been meaning to do this for a while, but never got around to it . . . And I got scooped a little bit! Derek Flood did a couple of short videos about this and lit a fire. Thanks Derek!
Anyways a quick overview (as quick as I can do it, everyone else seems to have a better grasp of the brevity thing than I do) of how linear stuff embedded in Maya 2011/2 relates to what you may have been doing before . . . not expansive, just pointing a few things out.
*EDIT* Derek was kind enough to point out some of the specific bugs/weirdnesses he's found in the comments. Check it out if you're interested!
Maya/Mental Ray: Linear Workflow in Maya 2011 from zeth willie on Vimeo.
HERE'S (rt click, save as) the updated zbw_gamma script that works by shader selection and sticks gammas into the color channels. You can also adjust any/all gamma nodes in the scene or delete them globally.