Thanks! But too late. That machine died this time last year, after 6 years of excellent service. I moved on to new hardware.
Hopefully the xorg.conf is useful to someone else.
I've just looked up what people are saying about DebugWait, and I see the font corruption - that's just one of the types of corruption I saw!
But perhaps that was the only kind left by the time my laptop died.
Just a note to others, that DebugWait doesn't fix the font corruption for everyone according to reports. But, it's reported as fixed by the time of the kernel in Ubuntu 13.04 according to https://bugs.launchpad.net/ubu...
I stand by my view that Intel GPU support never quite reached "excellent" because of various long term glitches, although I'd give it a "pretty good" and still recommend Intel GPUs (as long as you don't get the PowerVR ones - very annoying that was, that surprise wrecked a job I was on). Judging by the immense number of kernel patches consistently over years, it has received a lot of support, and in most ways worked well.
Getting slightly back on topic with nVidia: Another laptop I've used has an nVidia GPU, and that's been much, much worse under Ubuntu throughout its life, than the laptop with Intel GPU. Some people say nVidia's good for them with Linux, but not this laptop. Have tried all available drivers, Nouveau, nVidia, nVidia's newer versions etc. Nothing works well, Unity3d always renders ("chugs") about 2-3 frames per second when it animates anything, which is barely usable, the GPU temperature gets very hot when it does the slightest things, and visiting any WebGL page in Firefox instantly crashes X with a segmentation fault due to a bug in OpenGL somewhere, requiring a power cycle to recover properly. So I'd still rate nVidia poorer than Intel in my personal experience of Linux on laptops