The story started out very simple and easy enough to follow--travel the worlds, find the feathers, cute romance-y moments etc. Then everything hits the fan and at first you're like, "Oh, cool, this is actually serious!" Unfortunately, being serious can only be so good for so long when suddenly, EVERYTHING is dark and depressing and there is NO RAY OF HOPE. The story also becomes extremely confusing and hard to follow when the same plot device is used again and again. Everything seems to drag on because of these two negative factors, and so what was a cute and adventurous series turns into... something rather terrible. There is almost a redeeming factor in the ending but that also turns out rather bad.
Art:
CLAMP has excellent artwork as always. The characters' limbs are a bit on the noodle-y side, but I suppose you can take that as their artistic trademark currently. (Not like the same could be said for their older series, but I digress.) Expressions are very animated and lively, though I think this quality went down a bit in the second half of it.
Character:
I'm sure many people picked Tsubasa up solely because it was featuring the beloved heroes of Cardcaptor Sakura. The fact that there would be additional cameos must have been an added bonus, and it was. However, the characters do develop in their own right, marking them as different from their previous incarnations. The original characters always live up to the hype however and are not so easily shadowed by the known ones.
Enjoyment:
I enjoyed the series immensely in the beginning. Light-hearted action is always my type of thing. At first, I was also excited by the story's turn into a darker side, but everything dropped immensely for me during a particular arc in which the angst and emo seemed to go on forever. Add that to the fact that suddenly everyone was the same and we had weird time lapses or time freezes or something dealing with the fabric of the universe which weren't explained very well or transitioned into/out of neatly, and we get a very unenthusiastic reader.
Overall:
I liked the series when it was cute and funny and had nice adventures. I detested the series when it dragged on with the angst and overused plot devices. If you were reading it for the cute and fun, I would stop once things hit the fan and just read up the explanations on Wikipedia.
