OK, so I am the one who used them at the Nat's.
When they were new, they did run hotter. After 10 or so flights they did run cooler. The one thing you have to adjust for is the discharge curve they have compared to a Li-Po. They will land at a much lower voltage than a Li-Po, but you simply drop the min voltage level in the ESC to 2.9 ish volts. Without that change, I had some sags in power in the second corner of the hourglass on my bigger plane. It sagged right when it needed the power in the corner, but came instantly back up to power as soon as the corner was finished. I have used up to a 12.6*5 3 blade prop on it with no ill effect. I used Igor's 12*5 narrow blade prop on it at the Nat's.
The plane I used at the Nat's is about 720 in^2, and weighs 65 ounces, and runs on all of 70 feet of lines. It produced the highest score I have ever received at the Nat's, in qualifying, at 614. That was in near stunt heaven air on a cooler morning. It used 2050 mah out of its 2600 capacity. Not even close to being an issue. Then in the top 5 flyoff, it flew in 24 to 25 mph wind, and did very well. I was very happy with its performance. This plane clearly flies better with this battery compared to a Li-Po. I did numerous back to back tests comparing this battery to both 5S and 6S Li-Pos. It is neither a weight or voltage issue that makes it fly better.
I do use an Igor active system, but this year I ran it fairly "flat" with a sensitivity of all of 12 in the wind. The sensitivity was at 10 for the 614 flight. Lap times were measured by several sources at 5.35 sec/lap, both in the calm and the strong wind. So, I can not answer any questions about how well it responds to a higher sensitivity and its ability to boost and brake, other than what I have observed at 10 or 12. It is just enough sensitivity to know that it is "just" working, but not overdoing it and speeding up in the wind. I was flying with David on Monday morning in 20 mph air, measured, and there were many comments on how well it "held back" in the wind. In other words, it resisted speeding up much more noticeably than some 75 powered planes....
They do have a different shape then the Li-Pos. You will have to adjust your battery mount for this. I run mine in the 3*2 lengthwise configuration. 3 cells forming a triangle shape, with another 3 stack triangle aft of the first. Long and skinny. This exposes more of the surface area of the cells casing to the air flowing by, and runs cooler than a 3 by 2 "brick". Your choice, but my long and skinny packs come down at around 120F. I do make sure there is plenty of air flowing by the ESC and batteries.
So what is the big advantage. They weigh 303 grams. That is less than a 5S2800 TP LiPo. It is nearly 60 grams lighter than a 6S2800 TP Lipo. That IS something worthy of consideration!
If you are using 6S2800 batteries, a switch to these is a real no brainer. Dane Martin can supply these to you for about $50 a battery. For $50, it sure would be worth the effort to try one.