I was totally new to Hearts, so heres my perspective.
First, Hearts itself is a frustrating game in that fortunes are quickly reversed by a few "gotcha" rules that, unfortunately, arent all spelled out in the brief help. Theres a point bonus of 50 points if you end a round with exactly 50 or 100 points. "Shooting the Sun" means winning all 13 tricks (like shooting the moon, only winning EVERY trick) and adds 52 points to everyone else.
I find myself restarting a lot, which consistently crashes the game if done during the trick-end point tally. There also are a few display glitches with cards briefly appearing upside-down or overlapping incorrectly.
I love the Letterpress-style aesthetic, but I wish there was a theme that included regular suit symbols, as the geometric ones still throw me off if Im playing quickly.
As someone else mentioned, the AI is very good at shooting the moon and yet wont do a thing to stop other players from doing it. So if the AI starts accumulating points, its up to the human to stop them.
Lastly, this app is virtually impossible to find on the App Store. Searching "Hearts" and "Hearts App" doesnt work for me and I had to resort to web searching a review. Cant blame the developer for that, but they should probably complain to Apple.