While it looks easy on the outside, it really isn't. The trick is to figure out which of the cut-outs the star can be removed from. I must admit that I solved this puzzle through trial and error; well I suppose then again quite a lot of puzzles of this genre are solved this way anyway. After quite some time trying all the 4 cut-outs, I managed to get the star more than half way out through one of the cut-outs (by chance really) and figured that probably is the correct one. And I was right; with a bit more manipulation, the star practically fell out.
What was more amazing was how easy it was to slip the star back into cage through the cut-out again, literally in a matter of seconds, as compared to the time it took to extract the star! After the star went in, it took me quite a while to get it back out again. The odd shape of the star obviously adds a lot to the difficulty.
Hanayama rates the puzzle 3 out of 6 in terms of difficulty but I think it deserves a 3.5 maybe. It takes a while to get the hang of gripping one of the points of the star and slowly turning and easing it out of the cut-out. With practice, one can solve it repeatedly and I managed to do it several times quite quickly. There are two other write-ups on the Cage so you may also want to look at Brian's and Jeff's blogs.