I do not know what went wrong after 10.5.6. Here is some history. I have a Dell Mini 9 in addition to my Dell Mini 10v. When I first installed 10.5.6 on the Mini9, the mirroring worked automatically without any need for these hacks. (Works = the screen on the mini was what appeared on the VGA out as well).
Then I upgraded to 10.5.8 on that. Mirroring went haywire (crazy screen) and I had to use command line / voiceover or a hack from some website to fix it.
Now, my Dell Mini 10v cannot handle mirroring either (using 10.6.2). Actually, /Extra/bin/mirroring on and off both screw it up for me - mini screen borked and the VGA out borked.
What broke mirroring in the first place ? Was it Apple messing up the Intel 950 driver ?