Sneak attack training adds +1 sneak attack die per rank. Since there is 4 ranks of this, we end up with 1d6 more sneak attack than previous. However, as Sephiroth noted, the static +3 sneak attack damage per rank ability that is currently available to all rogues on live currently (which is also, confusingly enough, called Sneak Attack Training) is absent. So, even with the extra d6, it is actually a net loss of sneak attack (unless we go digging around in other trees, which may not be possible due to enhancement tree limitations, for instance on an 18/1/1 multiclass)