MSDN & Apple say you can specify units in "s" or "ms" while Mozilla, Opera & the spec give "s" in their examples:

[MSDN](http://msdn.microsoft.com/en-us/library/ie/hh772285\(v=vs.85\).aspx)
[MDN](https://developer.mozilla.org/en-US/docs/Web/CSS/transition)
[Opera](http://dev.opera.com/articles/view/css3-transitions-and-2d-transforms/#introduction)
[W3C spec](http://www.w3.org/TR/css3-transitions/#the-transition-delay-property-)
[Apple](https://developer.apple.com/library/safari/documentation/InternetWeb/Conceptual/SafariVisualEffectsProgGuide/AnimatingCSSTransitions/AnimatingCSSTransitions.html)

Seeing as you can do "ms" through decimals in "s", shouldn't "s" be the best choice?