"Worth it" is completely subjective and different for each person. The Dessert Party is definitely fun and a very nice splurge. But it is possible to see WOC with good viewing from each viewing section: free FP, regular dining package FP, and the Dessert Party. AND the risk and possibility of poor viewing exist in all those sections, too. We've done all the sections and had good-to-great viewing in all. You are looking at an inverse ratio of price:wait time -- more $$ = less wait time, more wait time = less money/free. Only you can know which option is the best fit for you.
Free FP: biggest pro is the price tag, but this option requires the most time investment for the best view (about 90 minutes) -- and the view can be very good.
Regular Dining Package: WCT area is up front/CCR area is further back -- advantage here is that you get a full meal for the price paid (which is a big deal for some people) -- and if you were planning on dining at these restaurants anyway, why not get a WOC FP thrown in? There is some wait time involved, but not nearly as much as with the free FPs, and the views can be very good, too.
Dessert Party: good-to-great views overall (but there is a risk of poor viewing -- we've had reports of this), but the price tag is high, and the desserts aren't to everyone's liking. Minimal amount of wait time compared to the other options. Be aware that if you are a small party or solo, you will probably be seated with another party. This is stated on the webpage.