My friends and I have semi-regular game nights when our schedules allow and Carcassonne has become a welcome addition to the game rotation.
One of the best things about the game is its simplicity. Playing just one time will allow you to pick up the gist of the game. However, that does not mean that the game lacks depth. The game requires though on how best to place your meeple and though the element of luck is ever-present with drawing tiles, a good strategy can make or break your chances of winning the game.
Another major positive to the game is that it doesn't require much time, at least compared to some of the other games we play (Trivial Pursuit, Risk, Monopoly, etc. which take an entire night to play just one game.) You can easily fit a 3-5 person game of Carcassonne into an hour or less.
It is also accessible to all age groups. I play with my 20-somethings friends for the most part but have also played with my 50-somethings parents, with everyone able to understand and enjoy the game. The game is even simple enough that I presume children could pick it up rather easily as well.
I only have the first two expansion sets currently (Inns and Cathedrals, Traders and Builders) and highly recommend both as great additions to the main game. Each adds additional elements of strategy, though I recommend learning to play with just the vanilla game until you get the hang of it. I only spent around $40 online on all of this, so it was a cost effective investment as well.
Overall, Carcassonne definitely gets my recommendation for being a fun, (relatively) quick, and easy game to pick up and play.