As the people have said before, Cunning Brilliance is a 19th level ability that has no place in a 10th level SGT. Most threads about Factota I have read are either derailed by discussion of CB (OMG!!!11 its teh haxors- that factotum is almost as powerful as my wizard for one minute per day!!!1) or Cunning Surge (OMG!!!11 its teh haxors- that factotum can break the action economy as well as my wizard, despite not being as powerful.
Anyway... now that my rant is out of the way, here's my opinion on the (off-topic) Ex spellcasting dilemma:
The monsters in the MM5 have their racial spellcasting labeled as Ex. It means precisely nothing to class-based spellcasting, as abilities can easily have their types modified (think of all the ways to get spells as supernatural abilities or spell-like abilities, for example). And, in any case, getting spellcasting with CB is not that broken, because it only gives you 7th level spells at the highest, as it is a 15th level ability (or at least should be, if people take the other interpretation that the ability simply must appear on the table and use their Factotum level rather than 15).
2 more of my cp.