OK - found a Rage fix for texture popins on Radeon that actually works, for me at least. Game now plays flawlessy on my humble radeon 5750.
Do all the driver updates incl the beta driver then use the following shortcut parameters
"C:\Program Files (x86)\Bethesda Softworks\Rage\Rage.exe" +cvaradd g_fov 12 +com_allowconsole 1 +com_skipIntroVideo 1 +vt_maxppf 16
The key bit is the last one
+vt_maxppf 16
I picked this one up from an interview with id at the site below:
http://kotaku.com/5847710/id-explain...gs-coming-soon