Yeah I think this really sucks also. I didnt think I was buying a 120gb hdd for nothin, turns out i did. Surely they could put the option to install in? I mean if oblivion goty can have expansion stuff installed to hdd why not other games.
Before gta IV came out i assumed it would at least use the hdd for cache while playing, but i have read that it just runs off the dvd regardless. BUT while I only notice very minor pop in, my mate who doesnt have a hdd complains to me about the road disappearing alot and "lots" of pop in. Maybe hes just picky though, i dont know.
For me the road only ever flickers off in one spot between the first and second island ( over bridge towards second island where it curves right before toll booth). So it may well use the hdd after all. I have no problems with load times whatsoever, theyve all been pretty short for me.
Why oh why didnt ms go with hdd as standard, its ridiculous. It'd be great if R* came out with a patch with hdd partial install and some sort of pop in reducing and blur switch. Still a great game though, i still thought a next gen gta would look a little better or at least have no pop in whatsoever.