It's fun, but I've invested more time in Duelyst already, and feel like you have more control over your strategy in that other game (even not taking into account all the crazy RNG in Hearthstone).
Well, it usually feels like you have more control over your strategy in the game that you have been playing for a longer time, where you are presumably a much better player. I haven't tried out Duelyst and it might be true that you have more control over your strategy there, but I think that, in Hearthstone, you have tons and tons of control over your strategy if you know how to control it.
I agree with XP, a lot of the time it feels like whoever draws into a 1-2-3-4 is pretty much sure to win (of course, it depends on the matchup). Player 2 gets the coin and an extra card, so they have a reasonable amount of control over the early game, but Player 1 just seems to be at the mercy of the draw, IMHO.
The main differences are that in Duelyst:
-Both players start with 5 cards, can replace two of them before the game starts, and can replace one more at the beginning of each turn; replacing is guaranteed to draw a different card.
-Player one starts with 2 mana, player two with 3 mana. There is extra mana on the board, so you can sacrifice a bit of early game pressure to smooth out your curve. This means a lot more cards are playable early game (though if Player one somehow doesn't get a 2-drop or two 1-drops things look pretty dire for her).
-There is a board! The way you place your minions can be just as important, or more, than what you play. It also allows you to protect frail minions without needing Taunt.
It is true that I might be biased because I have been playing Duelyst longer.