Heres what I got from looking at all the specs.
Each bike has its own pros and cons. Overall I think that the Giant is the worst of the picks you have come up with. Usually I would recommend a Giant right off, but this one looks less than spectacular. Nearly every component is no-name or lower than those found on the other bikes. I have also ridden a Warp (last year's) and found it to be heavy on the scale and noticeably heavy when riding. The design also seems causes lots of pedal-induced bobbing.The Drivetrain is also noticeably lower-spec'ed than the other two bikes.
The other two bikes come with the same rims, front derrailluer, and shifter. The Cannondale comes with an XT rear derraileur as opposed to the LX on the Specialized. You also get
Shimano fully-hydraulic discs on the Specialized instead of the Cannondale-branded V's on the Cannondale. You get clipless on the Specialized as opposed to the clips and straps on the Cannondale. For Cranks, the Cannondale comes with "Shimano" cranks, while the Specialized comes with in-house Strongarm cranks. I have heard from people who are impressed with the cranks and Specialized's in-house stuff in general. The Specialized also comes with Specialized Roll-X tires. These have gotten great reviews in some of mags lately. The Cannondale comes with Hutchinson Scorpions. I haven't ridden them and can't comment. It would be worth a look at
mtbr . The Cannondale comes with the Manitou Black as opposed to the Manitou Axel on the Specialized. I'm not super-familiar with the Axel, but from what I know, I have the impression that the Black is beefier and intended for harsher riding.
The Specialized seems to have the majority of the better specs - The Cannondale only beats it in the rear derrailleur and the fork - not saying that the Manitou Axel could not handle your riding. Someone who knows the lineup of Fox's rear shocks and where they fall in order could tell you how those rate compared to each other. The Specialized's FSR suspension design is well-known as being superior to many. The Jeckyl's has had some criticism in the past, though a review of a more recent Jeckyl in one of the mags was not as bad as in the past. It will come down to which fits best and which company you feel most comfortable with in the end, but based on the specs I just researched, I would go with the Specialized. Raiyn has a version of the FSR and from reading his posts it seems as though he is happy with the quality. We've disagreed on recommendations of bikes and what we think of Specializeds in the past, but I'll go with the Specialized here. I'm still not totally crazy about some of Specialized's bikes, but out of the three you've picked it seems to be the winner without being able to tell which of the bikes will fit you better.
-Moab
Edited: To make it readable. I type too fast.