I don't know if there's a spoiler tag, or how to use it, so my apologies. Don't read on
I thought Jade was a good character, for the most part. I liked her interactions with Porco Rosso. The rest of the characters were shallow (the good/evil/good guard) or forgettable (I've forgotten if there are any other characters). I also had a big problem with the end plot, especially the Jade plot twist.
With a name like "Beyond Good and Evil", you'd think that some moral uncertainty would be eventually injected into what appear to be the bad guys. During the game there are certainly hints that there might be. Not at all. At most, we get a little bit of cutscene that threatens to turn Jade into a bad guy but it's obvious that this is just a hollow threat.
In the end, the game turned into "Just Good and Evil". Sigh. Nicely polished gameplay, though.