I have the FSA carbon team issue crankset with an ISIS bb on my hardtail and it is great, this is my third season on the crankset. I also have an FSA carbon K-Force Mega EXO crankset on my full suspension and it is awesome. Heck, I even have an FSA carbon pro team issue double on my roadie with an ISIS bb. Now, with that said I have to say that I believe the best crankset for the money is the Shimano XT with outboard bearings. I don't believe it is worth the extra money to go with the XTR.
I have no intentions of ever buying another crankset that uses either ISIS or octalink bottom brackets. I am lucky to get one season out of one of those bottom brackets. I have had three race face ISIS bottom brackets, two FSA ISIS bottom brackets and one American Classic ISIS bottom brackets. I have also had a couple of Shimano octalink bottom brackets. None of them last. I think external bearings is the only way to go.
Oh, the reason I would go with the shimano xt over the fsa carbon K-Force Mega EXO is simply price and weight. Unfortunately FSA lies about the weight on their crankset, it actually weighs 101 grams more than the advertised weight. When you consider the real weights the shimano does not weigh that much more at all and costs almost $200 less.
I may be fat but I'm slow enough to make up for it.