MNSSHP is fantastic. My brother and mom went for the first time a few weeks ago.
Going with my sister and mother in late April/early May of 2015.
I went to the not so scary one in September when I visited WDW for the first time. In Disneyland they don't call it not so scary. They are essentially the same party, though. Although last year, DLR gave out "healthy" candy in addition to MnMs, Snickers, Kit Kat, etc. Things like dried apples, pretzels, goldfish, cliff kids bars, cliff kids fruit twists, raisins, carrots, etc. It was nice to get both healthy and junk foody, actually. Disney World didn't do that.