Steve,

They're basically a lenticular shaped, carbon-over aluminum chainring. They'll be heavier (a dozen or two grams, here) but if you're looking for something that screams "I'm here to party, let's get down" they're hard to beat.

They are NOT what I would call a carbon chainring. Those are for WW idiots (the idiots among the WW crowd, most of whom are just fine).

FSAs are pretty commonly found on TT rigs. I'll be using a 54t during crits/hilly RRs this year, to force me to keep my cadence up, but give me a nice weeee little bit extra on downhills.