I've got a Lenovo U330 with Intel 4500MHD and Radeon 3450. I've been using kernels from the drm-radeon-testing branch for the extra radeon goodness of them. I used vga switcheroo to alter between the energy efficient Intel and HDMI-enabled Ati cards. It worked ok until kernel from 20100521.
My previous kernel was from 20100511. When I switch to the Intel card (I must do DDIS, to turn on the radeon card and later DINT to turn the Intel card on) I get a 100% CPu usage from kslowd000. If I try to switch cards once more I get a kernel freeze.
I reported it to the kernel bug tracker:
Has anyone had any problems with vga switcheroo? I ask because not one of my vga switcheroo bugs got any attention
It's unfortunate that the vga_switcheroo had been introduced and largely forgotten It worked really nicely when Airlied introduced it. It seems that noone cares about it anymore