Just to add...the first parade is busier than the second. As you get closer to Halloween the crowds might be a bit heavier, but keep in mind the trend stays the same. And we found that you do need to set up about 30 mins to the parade for a good variety of seating options. (Sometimes earlier depending on the time of year, night of the week and where you're at in the park) Well worth it!
We've watched this from Frontierland and Main Street and both areas are good viewing for the parade.
This is one of the best parades at WDW. With it's fun music, you just can't help not having a good time.
And don't forget Hallo-Wishes in between the two parades, which is a must as well.
If you have not ever been to MNSSHP this is definately worth the money!
Have a good time.