For almost a year, I gave Magic the Gathering a try. I enjoyed the game, it is well designed, relatively fun, extremely well supported, and the players are plentiful. However, the trade-off in my eyes was twofold.
The first issue with the game was the general player population. I played in a few organized events at my local gaming shop, and generally speaking didn't have any fun. The players were far too competitive, and generally not that accommodating to the newer players. I certainly don't mind losing, because in any game someone has to lose in order for another to win; but good sportsmanship goes a long way there.
The second was the frequency of set releases. As a casual player I simply couldn't keep up with the number of new cards, their interactions and combinations. Having to at least be familiar with a new batch of cards every three months is simply too much work in my opinion; that being of a casual player.