Again don't quote me, if you have more detailed info on the cycle refreshes since 1998 I'm all ears.
The AIO CRT - 1998
Lampshade - 2002
L-Bar (White) - 2004
L-Bar (Aluminum) - 2007
L-Bar (Aluminum) With Edge To Edge Glass And Slightly Less Chin - 2009
Barring fairly minor details, the exterior design's unchanged since the G5.