This is the performance I am getting with my MacBookPro 2.17 GHz, Ubuntu 8.04 and drivers from https://launchpad.net/~tormodvolden/+archive

ati driver git 20080510 with XAA
Code:
GtkEntry - time:  0,09
GtkComboBox - time:  6,56
GtkComboBoxEntry - time:  5,45
GtkSpinButton - time:  0,85
GtkProgressBar - time:  0,49
GtkToggleButton - time:  2,63
GtkCheckButton - time:  2,62
GtkRadioButton - time:  3,15
GtkTextView - Add text - time: 12,25
GtkTextView - Scroll - time:  7,87
GtkDrawingArea - Lines - time:  1,15
GtkDrawingArea - Circles - time:  5,35
GtkDrawingArea - Text - time: 28,90
GtkDrawingArea - Pixbufs - time:  3,52
 --- 
Total time: 80,85
ati driver git 20080510 with NoAccel
Code:
GtkEntry - time:  0,09
GtkComboBox - time:  6,43
GtkComboBoxEntry - time:  5,22
GtkSpinButton - time:  0,82
GtkProgressBar - time:  0,48
GtkToggleButton - time:  2,57
GtkCheckButton - time:  2,57
GtkRadioButton - time:  3,05
GtkTextView - Add text - time: 12,76
GtkTextView - Scroll - time: 51,05
GtkDrawingArea - Lines - time:  2,05
GtkDrawingArea - Circles - time:  7,77
GtkDrawingArea - Text - time: 28,43
GtkDrawingArea - Pixbufs - time:  3,51
 --- 
Total time: 126,79
radeonhd 1.2.1 driver with XAA
Code:
GtkEntry - time:  0,09
GtkComboBox - time: 25,78
GtkComboBoxEntry - time: 15,74
GtkSpinButton - time:  0,93
GtkProgressBar - time:  0,54
GtkToggleButton - time:  2,82
GtkCheckButton - time: 11,97
GtkRadioButton - time: 12,83
GtkTextView - Add text - time: 16,61
GtkTextView - Scroll - time:  7,70
GtkDrawingArea - Lines - time:  2,40
GtkDrawingArea - Circles - time: 25,24
GtkDrawingArea - Text - time: 28,60
GtkDrawingArea - Pixbufs - time:  3,54
 --- 
Total time: 154,79
radeonhd 1.2.1 driver with ShadowFB
Code:
GtkEntry - time:  0,09
GtkComboBox - time:  7,16
GtkComboBoxEntry - time:  5,90
GtkSpinButton - time:  0,83
GtkProgressBar - time:  0,48
GtkToggleButton - time:  2,66
GtkCheckButton - time:  2,84
GtkRadioButton - time:  3,55
GtkTextView - Add text - time: 12,34
GtkTextView - Scroll - time:  7,18
GtkDrawingArea - Lines - time:  1,35
GtkDrawingArea - Circles - time:  3,90
GtkDrawingArea - Text - time:  3,90
GtkDrawingArea - Pixbufs - time:  0,25
 --- 
Total time: 52,43
The best choice is radeonhd with ShadowFB.

A question: why not making ShadowFB the default on radeonhd?