It would be interesting to see if the storage device makes a difference in loading textures. For example testing the difference in the game 'Rage' comparing different storage devices like trying it on a 5400rpm hard drive, 7200rpm drive and a SSD device.
I bet an ssd with such lower latency would see less gfx issues with regards to the megatexture technology.
My experience running RAGE (I have it installed on a Crucial M4, which is also my system drive) is that the texture popping still occurred, despite the fact that the SSD is very fast. I only was able to reduce the popping by making tweaks to the .cfg file and in Nvidia control panel. I don't think it has much to do with drive speed.