The X.org radeon driver continues to be very stable with Mesa 7.7 and a newer libdrm (2.4.17), and now I'm running the Linux kernel 18.104.22.168. When building it for the first time, I enabled ACPI S3 suspend (to RAM) support in the configuration because I had initially planned to try it with the kernel mode-setting drivers (that part of the plan got scrapped when I found out that the KMS drivers are not intended to work well for 3D yet) — so, after rebooting, I noticed a new button in the power management widget in KDE's panel.
A shiny new button... S3 suspend had not worked for me during all this time because uswsusp and the kernel were unable to bring the keyboard, touchpad and screen back to life when resuming normal system operation, so I had disabled support for it in the configuration for many kernel versions for fear of accidentally suspending to RAM instead of disk, and losing my current work as a consequence.
However, the power of Debian Squeeze's current hibernate script package (?), the vanilla+TuxOnIce 2.6.32 kernel, and all the new graphics drivers, seems to do miracles. Suspend-to-RAM works at last on this laptop! After a year of fiddling with build and run-time kernel configuration and tools! (And this is why it's a bad idea to run Linux on a brand-new laptop; but I knew it was going to be like this and still went ahead, mind you.)
This means that the ATI mayhem is over (well, except for a little problem), and now that I can run some of my favorite OpenGL-based software, suspend to RAM and disk safely and run KDE 4,
my mission is complete my work here is done. My local builds of this software are my very own Christmas gift this year.