Safari 3.1 (Mac/Win) : yes, but no multiple shadows
Safari 4 (Mac/Win) : yes, full support
Opera 9.5 (Mac/Win/Lin) : yes, full support
Firefox 2/3 (Mac/Win/Lin) : no
Firefox 3.1/3.5 (Mac/Win/Lin) : yes, full support
Google Chrome 1 (Win) : no
Google Chrome 2 (Win) : yes, full support
IE 7/8 (Win) : no
Shiira (Mac) : yes, but no multiple shadows
Konqueror (Lin/Mac/Win) : yes, full support
iCab (Mac) : yes, but no multiple shadows
Epiphany (Lin) : yes, since April 2008
Safari on iPhone : yes, but no multiple shadows
Nokia Symbian-Smartphones (Series 60) : yes
Opera Mini 4.1 : yes, no blur radius