Not terrible.
It’s biggest failings are in the culling phase. There is no way to quickly swipe between photos to A/B them and decide which to keep. To do this you have to mark one photo, then tap full screen preview, exit full screen preview, unmark the photo, and do the same with the next photo, and by now you’ve probably forgotten what the previous one looked like. Obviously this is even more problematic when there’s more than 2 similar photos in a group.
I consider the ability to easily A/B the photos pretty essential to this kind of app.
Also, sometimes when you preview the photo, it won’t show it in full resolution, it will just enlarge the thumbnail into a blurry useless mess, which is no good.
There’s potential here, but it’s got a long way to go before reaching it.