Most of the local racers around me are riding 100mm dual squish XC bikes...and this year looks like the top choice is the Trek Fuel 9.8 (Niner Jet 9s too), which is only 500 bucks more expensive than the ProCaliber 9.8 hardtail. That doesn't seem like a huge dollar premium for dual suspension to me, especially when the bikes in question are $4-5k.
Also, what bike is faster depends on what the terrain is like, even uphill. There is an advantage to having rear suspension even in climbing, especially if that climb is rooty and/or rocky.
Unless if I plan on XC Racing again, I don't think I will ever ride a hardtail again (I will race MX or Road Motorcycles before I do bicycle racing). I will always ride FS in one form or another unless if I am riding on really Smooth Trails like those in the San Francisco Bay Area, here, I would prefer a fully rigid bike over a hard tail. Actually, I am turning my Litespeed Hardtail into a fully Rigid Bike very soon. I have the rigid carbon fork on hand and ready.
I am open to change.... I really do want to say "FS are faster".. however, the results have not shown shown it. I have no say in any of this, all I do is observe and take notes.
I have heard the same thing since 1999 as what you said. That "FS could be useful for climbing", this may be true for a difficult section, but overall in a XC race, the RESULTS shows that Hardtails will come out on top (even now in 2016 this is the case).
Race RESULTS speaks for themselves. Even in 2016 (based on 2014 and 2015 results), we can see that hard tails still dominate the podium. Take every World XC podiums the past couple of years, add them all up, and it will be less than 10% wins for the hard tails. Until I start seeing all the podiums in a given year be more than 50% of FS, then I will still generalize and say "hardtails are faster". HOWEVER, that day has not come yet, so for now, I will keep my "Full Suspension bikes are faster" comment stored on my C:/ drive of my personal computer, and save it on there in a special place to possibly be used in the future (If this future ever comes).
As for myself, I don't like hard tails, they are NO fun and beats me up. I ride in very rocky terrain where even the "smoother" parts are very bumpy. I feel faster on my short travel Intense Tracer than my Hardtail, but I on my 10 mile normal loop, my times shows I am actually faster on the hardtail even though I feel faster on the FS. So it is obvious, whatever I lose through the rough, I more than make up for through the rest of the course.