That driver shows version 8.88.8 in the installer, 8.880 for the debs created. Basically it should be a 11-8 driver from that version. Sadly that driver is unstable. When i do absolutely nothing just KDE 4.4.5 (with effects forced on) the system crashes after a while. Tested with 3.0.1 kernel on Debian squeeze 64 bit, i7-880, 10 gb ram and of course AMD HD 5670. The driver can be installed using -vs option to my script, best combine with -z and reboot after install, short (as root)
sh install-fglrx-debian.sh -zvs
Should work with U too, but did only test on D. -z means no X kill (will usually crash fglrx), so preferred way.