Hi Everyone,
I just bought an iMac 20" with the ATI Radeon HD 2600.
I have been running SL for an hour and a half with no problems. Movement seems smooth and graphics are set near maximum, avitar imposters are off and the graphics memory is set to half of the 256MB available.
Sometimes I get a pause in movement, Im not sure if thats my connection slowing or whether its the viewer, will keep an eye on that and report back when I know.
So for anyone thinking of buying an iMac , the current model 20" with the HD2600 video chipset seems fine.