I got an invite yesterday. I played through the first two acts (need to do this to unlock the arena game mode) fairly quickly. Unsurprisingly, the AI is very bad, which made this a pretty tedious experience even though it didn't take all that long. It serves as a tutorial, which I guess would be useful for someone completely new to the genre, but anyone who has played any similar card games will find the mechanics extremely familiar (maybe even too familiar). It strings you along with cards and gold as rewards though, so you'd be pretty silly not to finish off the solo adventures unless you're planning to drop a ton of cash.
For an alpha/beta (my invite said beta, but in game it says its an alpha build) game it's in a pretty good place. Not buggy at all, plays very smoothly, and there's more card variety than I was expecting.
If you like Hearthstone but want a change of themes, you'll feel right at home here. A lot of the mechanics seem to be ripped straight from it (charge, battlecry, taunt, deathrattle, etc, just with different names) - though to be fair Hearthstone probably did the same thing. You have a deck, you gain 1 'magicka' each turn, and players alternate turns playing more/bigger cards as the game goes on. There is no direct action you can take during your opponents turn. Hero to lose all his health first loses.
There are some unique mechanics though. Well, unique compared to Hearthstone, I don't have much experience with other games in the genre.
Some of the things I like:
1. Rather than picking a hero/class and building your deck from just those (and neutral) cards, you pick two 'attributes' and can mix/match from those (plus neutral) cards. I think MTG does something similar. With only 5 attributes that only makes for 10 possible combinations (plus 5 more I guess if you count going all in on one attribute), but I feel like it adds more room for innovating on different decks and play styles compared to Hearthstone. I could be wrong, but it's interesting enough to keep playing a while to find out.
2. There is a mechanic where you draw a card for every 5 points of damage your hero takes, and if that card has the 'Prophecy' keyword you can play it for free right there during your opponents turn (or just stick it in your hand, but it won't be free when you play it). So far I don't have enough of these cards to build around it, but I've had other players, and even the AI a few times, ruin my day with a poorly (for me) timed Prophecy draw. And it's not just the fact that you sometimes get to play a card in the middle of your opponents turn, it also adds a new dimension to the choices you make throughout the entire match. Doing a lot of damage early gives your opponent free card draw essentially (since they get to keep whatever card they draw regardless of whether it's a Prophecy card or now), which can be devastating if you can't keep the pressure on and finish them off. It manifests at the micro level as well in each round, you have to plan your minion placement, spell usage, attack order, etc, around the possibility of triggering a prophecy draw when you attack the enemy hero. I've only played a few hours and that was long enough to encounter multiple situations in which my careless planning caused me to lose a close game.
3. Rather than one play area for each person, the board is split into two lanes (imagine a vertical divider going right down the middle of the Hearthstone board). You have to choose which lane to play each minion in, and they can only attack other minions in that lane (and taunted or 'guarded' minions as they are called in this game will only protect against enemy minions in their own lane). Additionally many spells/battlecries/passive effects, etc, will only affect friendly/enemy minions within the lane they are played in. It creates a sort of double-front war where you have to split your limited resources carefully. I'm still just learning it, but there definitely seems to be room for various strategies and counter-strategies with this setup that just aren't possible otherwise.
Some things I don't like:
1. No weapons. Well there are weapons, but they are classified more generally as 'items' (and there are non-weapon items as well). More importantly, they can only be equipped on minions, your hero can't use them. I really like the way weapons work in Hearthstone, how they turn your health pool into a sort of secondary resource, spending health in exchange for board control. Knowing how and when to spend your health, how much you can afford to spend, how low you can risk going against each type of deck, etc.
2. Arena is basically the exact same as Hearthstone. It's entertaining enough for now since I'm just barely starting to learn all of the cards and combos and strategies, but eventually it will grow old just like it did in Hearthstone. I've given up on Blizzard ever making any improvements at all to arena, so it's sad to see that this game has basically copied the Hearthstone format exactly. All I can do is hope that arena doesn't become a forgotten game mode here as well.
Well there's more I could say but I'm tired of typing.