Milliseconds. Not enough for the average user to upgrade to. Do you run specific programs that need faster disk acess or are you just trying to upgrade your pc for general use?
If for general use stay with your current hard drive. If you later want to add another hard drive for more disk space and dont mind reinstalling your OS then go for it. Otherwise, dont waste your time.
BTW, just for general knowledge its 7200 rpm. If you find a 72,000 rpm you should upgrade. The time difference would be astronomical...
(no such thing as 72,000 rpm)
Also, if your running applications that really benefit from faster disk access then you will want to get to SATA drives and stipe them. This writes part of the data simultaneously to both drives reducing the time it takes to write the data.