And they were awesome. For a while. But later in the series there was never anything different that happened during the morphing.
"And then a feather pattern appeared on my arms and face, and then I got itchy as it turned into real feathers. And then my face pushed out into a beak like a thousand screaming zombies pushing up out of the ground. Also, at some point I grew wings and my eyesight got better. It was like I could see the tapeworm in Mr. Chapman's stomach from across town, only not really. Finally, I felt the cold, calculating mind of a predator, ready to hunt some mice, only instead of mice, I was going to use it to hunt evil brain-stealing aliens. Did I mention that morphing is always different and disgusting? I threw up."
After a while they went from being unpredictable and disturbing to just being the same filler that could be used every book.