Subscribe to OTH warfare and you will understand the importance of the tiltrotor to my brother Marines. The aircraft is going to have further teething problems no doubt, but the concept (if not the aircraft) is a strategic leap in warfare.
Another area is NEO operations. Study even just a bit about the embassy evacuation in Somalia in 1991. The mission was accomplished, despite the equipment available, not because of it.
Even in short range operations there is a large advantage to faster, more capable aircraft. A few minutes may not seem much to an armchair quarterback, but could be the difference between life and death to a grunt in a firefight.