Thanks guys! I've acctually had a few successes sence I wrote that post.
I mostly got into using the liquid stuff because of my grandmother, who remembered her grandmother making watermellon jelly---which I figured would make a nice Christmas present. But, the only recipes I could find asked for liquid fruit pectin, which hasn't been around very long, but was worth a try. I will say don't use the stuff that Ball makes, their powder pectin is good, but their liquid pectin needs work. I tried Certo after several bad batches with Ball and got a good jell out of a Kiwi jam, and a White Peach Lavender Jam. I'm going to try the Certo with some watermellon Juicy Juice next time and see what happens.