Expensive, Vulnerable and Useless.
The Marine Corps disagrees:
http://www.marines.com/operating-forces/equipment/aircraft/mv-22-osprey
They rolled that out what? 1988?
The p-51 Mustang took 23 months to design, build and roll out.
http://www.mcclatchydc.com/2013/05/09/190817/reputation-remake-tilt-rotor-osprey.html
FWIW, the USMC seem to like it in the field.
USAF seems to have liked it here, at least.
http://www.forbes.com/sites/beltway/2011/04/04/the-much-maligned-v-22-osprey-is-confounding-critics/
It was hell to build, but it seems to be money well spent.