They can be used from 1-5 days. Implants feel a bit firmer than natural breast tissue. Depending on how much tissue you have naturally will also make a difference. Most men do NOT care, most probably wouldn't notice the difference anyway. See How Men Rate Implants .
Contracture can cause the breasts to feel hard.
Implants create a gap between the breasts. This gap does not occur in natural breasts, as they slope down from the center. Some docs prefer this so you won't move during surgery. However, make sure your surgery is in a hospital or accredited surgery facility. The JCAH usually accredits hospital facilities and hospital-based outpatient surgery facilities.