Typically, the harddrive is the coolest part of the computer next to the enclosure bottom. Does the 7200RPM HD really generate THAT much more heat than the 5400? I ask because I need to get a bigger 7200RPM HD for my MBP.
I read about it, before purchasing my 7200rpm drive a month ago, people said it would be louder, but I can't tell the difference. And the heat issue, i'm pretty much sure it's because I am aware that it'll be hotter, that I find myself checking it from time to time.
Seems fine on mine, doesnt get hot to the point its a problem. It does vibrate ever so slightly but thats to be expected!! It has a different feeling depending what surface its on, different types of wood for example, just worried myself now thinking my Macbook Pro likes different wood, ok lets not go there!!
In all seriousness thought I think you should be fine, dont worry about it unless your Mac is going into meltdown!!!