As a major fan of the original series (and also as a fairly on-the-fly idea) these are my thoughts, disjointed as they are, on the NEW Thundercats series now showing on Cartoon Network.
Sorry for the constant repetition and 'ums' and 'arrs' in the video, but I was talking completely off the top of my head with no scripting at all.
A couple of things that I missed out on in the videos:
Jaga! - How in Mumm-ra's scrotum could I have forgotten JAGA!!!! His character has really not changed. He is the old, wise and learned Thundercat who is the King's Head Advisor and also Head Cleric (Cheetara is also a cleric, training personally by Jaga, so this could lead to her having her visions again like in the original). He doesn't die at the beginning like in the original (that is reserved for another character), but he is captured by Mumm-Ra and Grune.
Romance! - I know.... WTF?! Basically, from the first few episodes, it looks like they are setting up a love triangle to break out between Lion-O, Cheetara and Tygra. Now I can kinda see where this is coming from, a lot of modern cartoon series have some kind of internal tension between the main group of heroes, as well as possibly wanting to cater a bit more to the young female demograthic than the original did.