The best thing about lumina is that it gives you full control over your images, allowing to change any aspect of an image without having to use Photoshop or other software at all! There are few things which can be improved but nothing major - I would say overall experience with this app was very good for me so far (I have used only one version).
It's easy enought even if not familiarized yet with photoshop/lightroom etc., as well there aren't many features offered by default like in some paid apps out there. Also no need of additional plugins required unless needed otherwise; works perfectly fine right from first try itself.