If you have never done it before, it is worth trying. Like what Drince mentioned, "worth it" is kinda of a personal preference, but one that you will only be able to decide on once you try it for yourself. We really enjoied ourselves when we went, but will most likely not do it again until GusJr gets a little older.
My take on it is that if you do go, do try to partake in many of the special events that go on as a part of the party. Of course, most of the attractions will be open at that time and the lines are rather short, for the most part. Heck, during the last hour of the party, most are walk-ons. However, in reference to this week's WDW update, there may be some concern about crowds since it appears that the party start time and the park closing time are both at 7PM. That in of itself is not a big deal, but since MNSSHP is a ticketed, extra event, getting all non-party-goers out of there may be a challenge. It ought to be interesting to see how things turn out. By no means should that be a discouragement to go but just something to keep a lookout for.
In any case, my tip for this is to go during a school night... crowds tend to be lighter anyway.
In addition to these comments and comments to come, you might want to do a search on "MNSSHP" to see some of the recent past conversations. You might get additional insight from those past posts.
Hope that helps!