Simply one of the best applications on the market today, and FREE (?) amazing.
So i was building a collage for a printed banner (3x6 feet) and thought "Hey, let's max this mother out". I set my canvas to 6x3 at 300dpi. Everything worked beautifully until I hit about 30 layers (of small-ish clips, each one ~40MB PNGs). My PDN file was 450MBs, and loaded up clipped out at ~27GBs RAM (I have 32GBs, i7 2.9GHz, +4GB Quadro M2000M, it's a strong laptop). When I added the ~31st layer it freaked out and crashed. Repeated reboots / attempted downsampling to 150dpi, "flatten image", nadda. Everything spiked through the ceiling on the RAM and crashed the app. I ended up resolving by flatten each layer one-by-one, and watched my RAM drop about 1GB per layer, until I got it down to just one flat layer (slowly). I was then able to add the remaining 10 layers, scale them, and export to a format supported by the website (max 50MegaPixel).
Though frustrating ... the tool produced an amazing result and over a decade of pleasure using it. I love you Paint.NET. Thanks.