Soldato
Thats the thing - it isn't a particular area or intensive scene, it *seems to be* completely random. Luckily it doesn't happen too often and is barely noticeable when it does happen - others have reported different though.
The 'stuttering' is due to paging - mainly from DRAM to VRAM.
If you check VRAM usage during gameplay, you'll see that it remains fairly low (around 450Mb in 2560*1600). As you move around city hubs and other large maps, you see occasional 'stuttering' as data is swapped out (some textures are removed from memory to be replaced by others).
Immediately after you load, you will often experience a more severe stuttering, just for a few second. This is HDD-> DRAM paging (as the textures are loaded into system memory). A precache would eliminate this type of paging, but would increase load times.
Anyway, a solid state drive will significantly improve the 'just after loading' stutter, but the stutter from entering new sections of a hub son't see any improvement from this. I suppose having a higher memory bandwidth will help with that, but I doubt it will eliminate the problem entirely.