I haven't been able to see all the episodes. I saw "The Sword of Omens" and "The Duelist and the Drifter." I'm a big fan of the original series. When I was 4, I had Lion-O toy and loved the 'Thunder thunder thunder' part, my parents won't let me forget about it. Seeing the original series as an adult, I realize how slow-moving and boring it was. the animation was so-so. In this new series, the animation is smooth and beautiful, but of course copies more anime and it looks more like Anime and can be confused for one. It too is slow moving and like the original series, not every episode is the thundercats versus Mum-ra. Even though the characters look similar, have the same names and personalities are more or less the same, their storylines have changed slightly.
Where we don't really sees Thundra in the original series, we see it in its full glory in the first episode. Tygra is now Lion-O adopted older brother, Cheetra is not well known to Lion-O, Panthro is believed to be dead, the twins are poor and not related (they don't know each other) to the others, Snarf is more a pet than a nursemaid and doesn't speak and Mumra has not been released--until the second episode. For older fans of the original show, they will love the carefully crafted homage and enjoy the twists turned to these old characters. But for newcomers, it might be confusing that the characters pay homage to a warrior they never seen or heard of in Panthro. Judging by the style and subject-matter I think children 8 and up will enjoy it. I don't think it appeals to younger children. My 2-year-old nephew sort of ignored it. But I think it will have a slow-moving audience to build up into liking it. Many kids love Dragonball Z (which is on Nick Toons and CW 4 Kids) but the colors are duller here than that so maybe it will take time to catch on.
The first episode I saw was "The Duelist and the Drifter," which in fact is the 8th episode and it only featured Lion-O and Snarf, as they went to a strange town and Lion-O fought a duelist who takes swords from loosing duelists. A strange floating rabbit-like drifter gives him strange riddles and warns him not to duel the duelist. Lion-O is hard headed and looses the Sword of Omens. Lion-O discovers that the strange drifter is the one who created the sword that the duelist wields and asks for his help. It is a great episode, even though you know where it is going and the storyline is a bit played out, it is charming and great storytelling. "The Duelist and the Drifter" can stand on its own but does supply growth in the character of Lion-O, which does capture the spirit of the old series. Hope we don't see those robo bears form the original, they remind me too much of Ewoks.