Widely regarded as an almost complete waste of talent points. Fade works as an "oh $#@%!" button that temporarily reduces threat that has already been generated (usually after pulling aggro off a tank) rather than a permanent threat reducing ability or a constant thread reduction, and additionally is only effective in a group situation. Almost no builds include this talent. Shadow Priests seeking to reduce threat are much better off taking the 2 points from Improved Fade and putting them into Shadow Affinity.
Prior to the Priest talent review, this ability increased the time Fade lasted by 5 seconds per point, thus with 2 points the talent formerly allowed Fade to be effective for 20 out of every 30 seconds (67% of the time), instead of the current 10 out of every 24 seconds (42% of the time). Thus, after the review the effectiveness of the talent was reduced by close to 40%.