I'll tell you what.I replaced an old XT(square Tapper) crank with a FSA carbon.I honestly felt no difference.I think it says something for both.So in my case the carbon was just bling.Oh,and maybe a few grams.Forget about it breaking.Formula 1 cars,the B2 stealth bomber,and the F-117 are mostly carbon fiber.NOT ALU.It just freaks me out that people are worried about carbon fiber breaking.Carbon fiber na-sayers got to get with the 21st century.
http://www.airforce-technology.com/projects/f117/ The F-117 is mostly metal according to this site. I couldn't find anything of this nature for the B-2 other than a mention of "composite materials" which doesn't neccesarily mean CF or use of it as the primary material. Formula 1 car are inspected for stress after every race and are not used for the entire season.
I too run CF components, but my point in my first post was that it doesn't take the abuse metal will. If you run CF parts you have to account for the possibilty that if you take a chunk out of that crank, you need to replace it.
Is it an upgrade...Yes.
2013 DeVinci Leo SL
2012 Niner Air9
2009 SE Racing SoCal Flyer
2003 TiSport Gman
One thing to consider here is the price difference. Where I come from the Truativ crank you refer to is double the price of Shimano XT. Of course it's better, and it's an upgrade, but is it twice as good? Personally, I don't think so, even if it doesn't crack.