Yes there are shorter lines for the attractions(marginally, until late)But the lines for the special bits are out of control. You might wait 75 minutes to meet a special character.
I will say I had a blast and thought it was my best time at the magic kingdom, but I don't do character meets.
It's also a good chance to meet characters who aren't ordinarily out for M&Gs in the Parks (i.e. Scrooge McDuck, Abu, Moana, Nick & Judy) and even some in exclusive outfits! Tip - meet more elusive characters towards the beginning of the party (heck even before it starts) or after the fireworks.
We've only done the Xmas Party 2x, once when we only had one kid, who was only a baby. Our trip also coincided with one my sister took with her family and our mom. We didn't do any characters. Lines were short for attractions but the place seemed packed; I only assumed that while only people with wrist bands could get on attractions, see special shows, get the added cookies and cocoa, they weren't kicking anyone out of the parks who wanted to stay and see the parades and the fireworks, because hey, shops are open. So it did feel packed.
Now, the second one we went to, we had both kids, Slapperina was 7 and Slappetina was 4. We had no intention of going originally but we're suckers. And we had a great time, BUT the one thing I really regret was when Slappette saw Judy and Nick from Zootopia and decided we needed to be in that line because the kids loved the movie. It wound up being 90 minutes of our 5 hour experience. Nick & Judy "took breaks" twice in that time. And while up to that point my kids were always scared of fireworks, suddenly they really wanted to see them, and of course they started while the line was almost done. So we missed the beginning, got pre-printed autographs and a quick photo. We all agreed it wasn't the best use of our time.
On the flip flop, we rode every E-ticket that night, and in fact I think we rode Mine Train twice, and my youngest up to that point had never been on Space Mountain and felt like a hero after it was done. I remember posting the pic on FB with the caption "there are no more worlds left to conquer."
So...I would concur, unless someone in your family is a rare character bloodhound that must have a picture taken with those usually mothballed costumes, don't use your time that way. We're in fact going to WDW this year at a time where we can do MNSSHP and the kids are already in strategy mode, what we'll do when, and tops on the list is do not make time for M&Gs.
