To me this seems to be a problem with Dell H/W rather then bug in intel driver. I tried this in Acer laptop with Intel driver worked like charm. Then trien on different Dell dimension laptop with nvidia (nv) driver, problem was there. Infact this time I tried even without installing X, and it was even worst.
While X is running, I was able to turn the display on by switching to TTy 1 and back to X. But when X is not running only way to turn the display on again is to reboot the system
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So I've tried this in 2 different Dell H/W, all of them having this problem and tried on one Acer H/W worked without problem.
So any one conscedring to purchase Dell Laptop for BSD might wanna conscider this.