The history of the program is failry political, and intertwined with many other programs and events. It goes WAY back to the AAH and UTTAS programs, which is what eventually gave us the Apache and Blackhawk.
At the time, AAH and UTTAS was to replace the AH-1 and UH-1 series. As both programs progressed into the YAH-63/64 and YUH-60/61 programs, cost overruns began to take it's toll (gee, like this has never happened before adn couldn't be foreseen). The Army came to realize that there was no way they could replace the aircraft one for one, or even one for two.
As a side note, both the Blackhawk and Apache were touted as being C-130 transportable, same as the Comanche is today, at about the same time in their development. Don't put alot of stock in what an unfielded system is "supposed to" be able to do. The M2/M3 Bradley was touted as "C-141 transportable" as well.
When the Army was faced with rising costs for the 60/64, they had to cme up with a cheaper way to replace the large number of legacy aircraft (i.e. the Bell products of AH-1, UH-1 and OH-58) without endangering the newer systems. If the Army came out with a cheaper system than the Apache and Blackhawk, Congress would start asking why were we buying those more expensive systems if a cheaper replacement existed. So the Army came up with a VERY complicated plan.
LHX was born. It was to replace the AH-1, UH-1 and OH-58. There were to be two versions, one utility and one recon/attack. Magically the Blackhawk and Apache no longer became replacements to the Cobra and Huey, but supplements (huh?). The Army identified a need to replace the now aging H-1s (which of course it had done a decade previously in order to get funding for AAH and UTTAS), and plowed ahead with the LHX program to replace the AH-1/UH-1 (whcih was supposed to be replaced by the 64/60 originally, but was now only being "supplemented" but them).
Originally, the Utility LHX would have one T800 engine and the Attack would have two. There would be some common parts, but it was quickly recognized that the program was becoming two separate ariframes faster than anticipated. As the program cost rose (gee, like that's never happened in a program), the Army axed the utility program and poured it's money into upgrades and the attack version (now called Comanche).
The Army has done a good job at politically justifying the Comanche, despite some various cutbacks during Clinton. They brought out the old saw about it being C-130 transportable (like the Apache and Blackhawk were supposed to be, and like the Stryker is supposed to be, and like any system is supposed to be when it gets into trouble) and the solution to modern warfare.
They armed the OH-58D to prove that an armed reconisance aircaraft had a purpose. At first when Bell proposed the program (I was there when it happened), the Army balked at it because the were scared that it would endanger the Comanche. If an OH-58D could do much of the job, why would Congress pay for the -66? Eventually, they went with it as a platform to prove the mission, and because they needed something flying now. It worked out well in that the armed OH-58D has proven the need, but is obviously undergunned. The perfect platfrom to justify the RAH-66.
So now there is no replacement for the UH-1, other than the Blackhawk (which it was originally supposed to do). The RAH-66 program has now gone too far to be cancelled, so it will mature and be used to replace the aging AH-1s left in service and the armed OH-58Ds. In fact the RAH-66 is a favored program now, because it's just about done, so there's little risk invovled with production. This makes Congress happy because they keep their districts filled with jobs and their pockets lined with defense industry contributions, so there's not much chance that program will get cancelled. The taxpayer has already payed for all of the expensive stuff, just production is really all that's left to foot the bill for.
So the end to this very long winded post is that the RAH-66 took a long and convoluted path mainly because of the politics of procurement. Nearly every weapons system program gets bought this way. This is why your taxes get so wasted and items cost so much.
Ross