My rating may seem too critical, but it's honest.  The mechanic of flipping a card to upgrade sounds great in principle, but really makes for a very poor experience when implemented.  Because the cards are two sided, shuffling becomes a very tedious and awkward experience.  You don't want to look at the cards while shuffling, because that would be cheating.  So you shuffle under the table.  But then if you drop the cards your current game is completely messed up.  It's a novel concept, but a horrible when implemented.