I just checked it again but I can blend every image just like a layer in Gimp/PS via following modes:
normal, add, subtract, difference, normal multiply, divide, multiply, screen, overlay, soft light, hard light, darken, lighten, color dodge and color burn.
Yes, you can add as many images as you want and "blend" them as you need, but you don't have Photoshop style layers to work on ONE image by itself. This is something that even the old DeepPaint 3D had ... a functionality similar to Photoshop's layering system.
So, in modo I can bring in multiple images, but in Photoshop I can work on multiple layers in the same image. This is missing in modo and many of us have been asking for it.
EDIT: Let me check into this. I may not be correct as I am usually only painting a single image in modo. In some areas of modo I know enough to help others. In other areas I am still a newbie

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Edit (again): See answer next post.
Regarding the crashes: Maybe I am one of the happy users.
I am as well, but I don't tend to push modo as hard as others. Most of my work is for real-time 3D, so there are a lot of modo's tools that I don't use.