It's a new and improved design. I like the new clicky feel of the 5 over the spongy feel of the 4S despite needing a bit more push.
-Apple's newest iteration of its classic home button sports an integrated metal support bracket, which we hope will greatly strengthen the oft-used switch.
-Many iPhone 4 and 4S users have experienced the woes of a faulty home button, but haven't been brave enough to attempt the repair. This new design should not only increase longevity, but also make replacing the home button a lot less of a hassle.