Like someone said above, overclocking will reduce the life of your processor, but I can guarantee you that you will be buying a new computer way before that ever happens (if done right of course).
If you provide sufficient cooling and you have a pretty solid processor, overclocking (within a reasonable amount) is nothing to be afraid of.
HOWEVER, I don't know if buying an OEM overclocked Gateway is such a great idea. Now-a-days you can probably get a better processor and build yourself something much nicer for the same price or less. Then, overclock at your discretion and give it some good cooling. I also think it's important to get yourself a nice, well designed case.
Or, just spend a few extra bucks and buy a faster processor to start with
