The same shape filled with a gradient renders differently whether it is rotated or not.
Created attachment 15041 [details]
A rotated rectangle with a gradient, works fine in Opera 9 and Firefox 3.
Created attachment 15119 [details]
This testcase found led me to something we failed to read in the spec, no objectBoundingBox mode when width and/or height is zero.
Comment on attachment 15119 [details]
r=me, looks sane enough.
Landed in r23650.