[sorry if there are a few "weird sounding" sentences in here: English is not my first language]
I'm new at playing modern boardgames, so this review is hardly from a trick-taking expert (I've only 1 match of Tichu and a couple of Mü under my belt; I can't compare this to Jass or Skat) or THE boardgaming veteran. What I'll write here are mostly my impressions of this game(no details on the rules of it: you can find that in other reviews), and how I feel it's actually not that crazy.
I bought this game on a whim. A friend of mine was passing through Germany and I asked him to buy a few cardgames for me (easy to carry). This was one of them. A fellow boardgaming enthusiast here in Brasília had mentioned this is by far the most absolutely crazy-insane-bizarre card game in the world. I, of course, was curious, so I added "cosmic eidex" to the small list I e-mailed to my europe-visiting friend. Once it arrived I downloaded the english translations (that won't fit in the box ) and asked the fellow who had already played it to teach me the game (always better than figuring it out by the rules alone).
We couldn't stop laughing in the first match. One of them got the Ace of Lizard power (you can switch your hand with an opponent if he/she agrees with you) and they kept switching it almost randomly. At the end of the game, however, I had a suspicion: this game isn't as tough as it looks.
A match with another group of friends of mine, with me teaching them, confirmed this. By the end of the first tournament, we had the value of the cards all memorized (usually 10-2-3-4-11, with the removal of the 2 and the adition of a 14-20 in the Trump suit. In Topdown or Bottomup, just add an 8) and we were playing pretty much naturally. Sure, the tactics of it sometimes stumped us (It can be hard wanting to win OR lose tricks, depending on your situation), but the game already had a good flow to it (the scoring after each hand still takes a few dozen seconds more than it should, though )
What is fundamental here is the fact that even though the value of the cards can (and probably will) change in a single 7-point tournament, throughout an individual 12-card hand it will always remain the same. That Trump Jack in your hand will still win over everything and give you 20 points (not taking into account the possibilities of Cosmic Powers). Even the Cosmic Powers remain the same throughout the match (which can be a drag, if yours isn't as powerful as your opponents; maybe a variant can be decided upon this...).
What I REALLY enjoy in this game is that there is practically no real "impossible" hand: if you have weak cards, you can go for the low score; if you have strong cards, you can go for high score; if you have an incredibly strong hand and see that it's almost impossible not to go over 100, you can try for a match result (win all tricks).
Another thing that can be easily overlooked is that you always have to watch your opponents: remember that in 95% of all hands, two players will win points. If you only worry about you being one of the two (and not caring who advances with you), you may be helping your opponent. This happened twice: the player that was obviously the less skilled one ended up winning, since me and my friend were after each other like rabid dogs and all hands ended up with one of us two scoring along with him. It's important to care who takes the trick if it isn't you.
Anyway, I rate this game something around 7, which for me is pretty high as far as "pure" card games go (you know, with kings and jacks and suits all; tichu is an 8). But you can print out the rules here and give it a try with a normal deck (just decide which "normal" suits correspond to the exotic suits in the game, in order to give out cosmic powers); I would definitely recomend doing so, and giving it a try (or three ), since some people really can't get over the switching values of it. Just have a little patience and it will seem even natural after a while. At least to me it already feels natural