As someone who has played an insane number of rogue type characters, including scouts (with the skirmish ability), I fully understand the problems and benefits associated with sneak attack and other forms of precision damage.
I do like the idea of it being used against forms of creatures that are immune to critical damage, such as undead, and the way they explained that it represented hitting weak points in a creature's form, not necessarily an artery or an organ. I do think, however, that during playtesting they'll need to tweak the amount of damage depending on creature types.
Perhaps humanoids and other common enemies would take normal sneak attack damage, whereas certain abberations or undead would only take partial sneak attack damage, unless a knowledge check in the appropriate field was made?
Someone earlier had suggested that a knowledge check be required to do sneak attack damage to an undead. While this might make some sense, it then basically says that a rogue has enough religious knowledge to apply it to other checks and the like. How many rogues do you play with that can sit down and have a theological discussion with a cleric?
If people wish to add any rolls to confirm sneak attack damage I would suggest either rolls depending on creature type, like I mentioned above, or perhaps a perception check against the monster's CR.