I have read lots of articles about 5200rpm drives and 7200rpm drives, but none specifically about this. I will be getting a gaming laptop (MSI GT70). It will have a120gb Samsung ssd and comes default with a 1tb 5400hdd. It would be $80 to upgrade to a 7200rpm drive. Sounds like a lot to me. Considering I have the ssd for the OS, would a7200rpm drive make much of a difference? It would really only be for storing games and cad files.
I wouldn't pay $80 for just a speed upgrade. If it were only $20 I'd jump on that, but the difference in responsiveness/performance isn't worth $80 at all. You probably won't even notice the difference since commonly used files will end up being cached anyways and programs you really use a lot will probably be on the ssd anyways.
Just a note, putting games on your hdd (as opposed to ssd) won't give you any performance boosts (maybe 1-2 fps) - it only affects loading times. The difference in loading times between 5200rpm and 7200rpm won't be that big either.