A quote from a Lt Col in from HMX-1 in the 90's running the V22 program..."the V-22 its neither a helicopter nor an airplane"
The resaoning behind tilt rotor goes back to the early 50s with the Bell XV-3 then in the late 70s with the XV-15. In between there were many experiments with tilt wing/ilt rotor not only in USA but in France and Germany and even the old Soviet Union....the old addage of vertical lift like a helicopter and fly like a conventional aircraft then hover and land like a helicopter. Like with the Harrier. I've seen it fly on video documentaries and close up at Farnborough and Fairford last year. Its neat.
The raison d'etre behind the V-22 is and was from the old JVX program (USAF, US Army (now pulled out), USMC, USN) for a tilt rotor that could carry more troops then a UH-60 possibly H-53 and fly great distances from the carrier battle group/ Marine Expedirionary assualt carriers to the beach and beyond the forward edge of the battle area. With in flight refuelling, great for self deploying from east coast of USA to Europe in theory in times of crisis. Or in todays world; lift off from say somewhere like Mildenhall (which will happen soon enough as the old MH-53M Pave LOw IV is being replaced by the spc ops CV-22 Osprey). and deploy without landing to trouble spots in Mid East or Africa without stop over in Sigonella or Akriotiri or Incirlik.
I dont know if you remember the ill fated Operation Eagle Claw ref Desert One the attempted hostage rescue in iran 1980? Studies done by the Department of Defence and Department of the Navy and private corporations such as RAND etc; said that if the V-22 had been around at the time the chances of a successful rescue would have been more successful.
1) No need for Forward Operating Base in the danger zone and if its not the bad guys its the weather tbat will kill the mission. So straight from the carrier and then
2) With reference to the above the less logisitcal support and the need to land the aircraft or refuel in the mid air, meaning time is reduced inherently.
3) The ability of the V-22 to take off and land vertically meaning it could have touched down on any of the buildings downtown Tehran deployed the Delta squads and rescued the hostages then taken off (with support of AC-130 Spectre gunships) less time in the danger zone, and more chance of coming home alive with hostages and rescue teams.
Yes there were a lot of problems and a few fatal crashes (mainly in 2000...first around MCAS Yuma ranges and near MCAS New River....) the technology still needs tweaking...because its fatcors like Vortex Ring State(VRS) = stall when blades spin too fast especially with the hovering.
There is also a civilian tiltrotor as you may be aware of the Bell Agusta BA609? And so far with the test flights and demo at Paris Le Bourget it has been a success.