TomsHardware performed a thorough review of a Seagate Momentus XT Hybrid Hard Drives. I recommend reading it.
http://www.tomshardware.com/reviews/momentus-xt-750gb-review,3223.html
Their conclusion:
"Really, the only time Seagate's Momentus XT slowed down drastically compared to an SSD was when we installed the operating system and applications. Once everything was fully loaded, however, performance rapidly improved as the drive's software algorithms pulled the most frequently-access data into flash, bestowing very SSD-like qualities to it. At that point, it was frankly hard to tell the difference during most common tasks. "
The radar plot at the end shows the mix of compromises, and the performance suggests it's worth a look if you're otherwise buying large capacity.
This has been the case since the mid-90s, when many professional EEs were being laid off and not backfilled.
So, it has to expand upon the existing system, and must deliver new function, and must be delivered on time, and on cost? That's an iron triangle and therefore must be waterfall, and with a ton of contingency.
Fire the project executive that picked Agile for that one....
Apparently you didn't know that, until recently, Scott Ambler worked for IBM.
Top Ten Things Overheard At The ANSI C Draft Committee Meetings: (5) All right, who's the wiseguy who stuck this trigraph stuff in here?