Since the weather is awful these days there's no chance for me to test-drive this app in a real SOTA outing, so I had to just play around with it in closed quarters. My regular SOTA app is Rucksack Radio Tool and here's a comparison of the two main screens side by side (SOTA Spotter on the right, RRT filtering SSB spots only):
To be honest, I already like SOTA Spotter's cleaner layout better. The settings tabs are also richer and they don't clutter the main screen.
Sending a spot is done from a different screen, wich makes sense as you don't really do that too often. It also remembers previous spot data so you only need to adjust what's changed.
Overall, I think I like it better than Rucksack Radio Tool. However, there is one major feature that will keep RRT my main SOTA app: it shows the nearest SOTA peaks and where / how far they are, wich is extremely useful when hiking.