Well, I've watched up to episode 4 online - ”Song of the Petalars,” and I must say, this new series isn't bad at all.
I don't remember the origins of the original Thundercats, but I like this new series, although the plot seems to be a bit cliched. It starts out with a young and brave prince Lion-O who's being groomed to be the future king of Thunderra. Their peaceful kingdom is attacked by the Lizard people, who use technology-based weapons and are working with an old enemy of the Cat people, Mummra. Mummra kills the king, Thunderra falls, and Lion-O inherits the Sword of Omens and gauntlet, thus becoming the new ruler of a now devastated kingdom. He's aided by his older brother, the more skilled and experienced Tygra, and a cleric who serves as a protector, Cheetara. They are joined by two street urchins, Wilykat and Wilykit, and Lion-O's pet, Snarf. Lion-O has to find the mystical Book Of Omens, which holds important knowledge and is also being sought by Mummra, whom Lion-O vows to find to avenge his father's death.
What I even like is the life lessons that Lion-O picks up along in his journey, such as the damage that hatred and revenge can do to a person in ”The Rise of the (Sea Creature)” - Moby Dick, anyone? In ”Song of the Petalars” Lion-O questions the shortness of life and its significance.
I like the anime style without looking cartoonish. The dialogues are often witty and sensible. And the character development, at least for Lion-O, is done pretty well.