Figure out if you get 1d6 sneak attack per inspiration point spent, or if you can only get 1d6 sneak attack period. The former is by no means broken, and the latter is nigh useless (with the sole exception of ability damage).

Not to mention whether or not any of the factotum's class features (including spellcasting, turn undead, sneak attack, and so on) interact with feats (like DMM), various items (like metamagic rods), and PrCs (like archmage).