So it's possible to do this today by specifying different transition-timing-function and transition-delay values with a selector with :hover, as Simon's reply in http://lists.w3.org/Archives/Public/www-style/2010Nov/0428.html indicates.
I propose that:
(1) the spec be updated to give an example of how to do this (since it's a common request), but
(2) that adding a feature for a better way to do it be postponed until the next level of CSS transitions.
http://dvcs.w3.org/hg/csswg/rev/2aeb262c2b49 does the former.
Probably LATER for the latter?