Free to play card battling game that is beautiful, easy to start playing, and offers a ton of replay-ability.
Ranked in these QuestionsQuestion Ranking
Pro Great even for casual players
Hearthstone has a friendly learning curve that makes picking it up and getting started easy for people who don't want to spend a lot of time learning rules and tricks.
Pro Brawl events, that don't require you to follow "the meta"
You can take advantage of weekly brawl events that give you a certain set of cards (so no need to pay to stay competitive). It keeps the game fresh, fun and fairly "casual".
Pro Active community
It has a lot of players due to Blizzard's fanbase which means finding multiplayer matches is not all that difficult.
Available on PC and on mobile. Makes a great commute companion (provided you have internet).
Pro Familiar characters from Warcraft 3 and World of warcraft
The characters used in Hearthstone are all from the lore of the Warcraft series, making for a familiar universe for fans of the series.
Pro Entertaining Voice Acting
The voice work really adds to the game and makes it entertaining to play.
Pro You won't be cursed at in the chat.
Interaction with opponent limited to simple pre-made phrases, so you don't have to see how many 1337 gamers had their way with you or your mother. Or deal with the spam about free decks, new hacks etc.
Pro Polished overall aesthetic
Possibly the most polished user Interface of digital CCGs. Unified and fun art style and flavor text.
Pro Great if you don't take it too seriously
HS is meant to be fun, lighthearted, and generally casual. It requires a lot of time and money investment if you wish to play seriously.
Pro Free to play that doesn't exploit
Yes it's free to play, but it's designed to easily continue to play and have fun without having to feel like you HAVE to pay. At the same time, after playing a while you'll probably want to.
Pro Card Balances and Game Updates Often
The Hearthstone team is always looking at their data and community reaction towards cards and the state of the game, and they have made many card and game changes/updates to balance and improve the game for all players.
Pro Near-perfect balance between going first or second
There's no significant first-turn or second-turn advantage in Hearthstone. The player going second gets an extra card from his deck as well as "The Coin", a card that gives one extra mana crystal for one turn. This subverts the advantage that would be gained otherwise by the player going first.
Con Huge Money Sink
Although you can "technically" play for free, Hearthstone is very stingy on rewards. To get the limit of 100 paltry coins free a day, you have to win 30 games vs mostly players who have much better cards than you. It can take a new player 6 to 8(or more) hours to accomplish this. And after all this you get a pack of 5 cards that are often completely worthless to any viable deck. It's possible to get cards like "Angry Chicken"(worthless card) as the "Rare" card several times. You can also get a bunch of cards you already have a lot of.
Con Many mechanics based on random numbers
Random effects in the game use a random number generator, which causes an uncertainty of all outcomes. This causes one or both players to be frustrated because they can lose an already won game despite playing to the best of their ability.
Con The reward system is not significant enough
Hearthstone's reward system is very lackluster, providing little to nothing of significance to the casual or excessive player. There will be times when you feel heavily rewarded by the game, but these times are few and far between and if you are driven by rewards you will likely lose attraction to this game quickly.
Con Lacking a lot of depth found in better TCGs
Con Additional "Cards" must be paid for if not earned by continuously playing
There is a bit of a grind in earning new cards, so for those that do not want to spend the large amount of time needed to earn quality cards they will need to be purchased, which can get expensive.
Con Crafting is expensive
In lieu of trading cards, this game uses a disenchanting/crafting system to handle duplicate copies in your collection and being able to obtain the cards you want. Many cards disenchant for paltry amounts, and the best cards cost lots of "dust" to be able to play with.
Con Ridiculously bloated
Over 4 GB data installed on ones device. Which is quite a lot of room, something many might not have to spare.
Con Simplistic and unintuitive card design
Very little mechanical depth, most of the complexity is based on random numbers.
Con Luck is more rewarding than skill.
When you lose a game in Hearthstone you don't learn anything because you generally can't play around most of the cards, most of the cards have random effects you have no control over it whatsoever.
Con Dependent on Battle.net infrastructure, not playable offline
The game requires a connection with Battle.net servers from the developers, and thus can't be played offline.
Con No trading with other players
Con Poor port
Plays much better on PC. Sluggish and crashes often on mobile, sometimes connections can be difficult to make as well.
Con Sometimes unfair matchmaking
Sometimes players will be matched up with people who clearly have been playing longer.
Con The discover mechanic alone ruined this game
Luck tends to be more important than skill: there are numerous RNG-based cards in this game. Players that care about skill are better of playing other games, like Magic.