Just remember type gets screwy.
By default Sneak Attack is just a bonus to your damage, if you're dealing fire it deals fire, if your dealing slashing it deals slashing.
However, you can also deliver Sneak Attack when dealing Ability Damage/Drain and Negative Levels. The damage type of your Sneak Attack is Negative EnergyRotG which can create some wtf moments. Like using a Constitution Damage based attack to heal someone with Tomb Tainted Soul. Best doctor ever.