First of all, its pacing and timing is impeccable, particularly in the comic scenes. The most important facet of comedy is timing; through the early episodes, Scrapped Princess is perfect. Second, the music is great. Watching Scrapped Princess, I appreciate that it has an actual musical score, as opposed to random bits of filler background music as you’ll find all too often. Third, this series is heavy on cliffhangers. Cliffhangers probably won’t impact your enjoyment of the show if you’re marathoning the series in batches, but when I was watching it for the first time, they certainly kept the anticipation high from week to week.
Now I wish I knew what to watch for. Cliffies can go to hell, but I did not even hear the music consciously. Oh well, water under the bridge.