I was a bit disappointed with Brilliance. Of course it's way better than DPaint, but I never found it that useful. For pixel art, I found PPaint easier to use.
DCTV Paint - by same company as Brilliance, but 3 years earlier - was unbelievable for the time. I think when DCTV Paint came out (1990/91), it would have blown away Photoshop on the Mac (which was primitive at the time). It came with the DCTV hardware which allowed 24-bit composite display on any Amiga. You could scan and paint 24-bit images, use adjustable transparency brushes, rub-through, stencils, blending, drop shadows. The only drawback was that DCTV Paint was for composite images only - not RGB.
I made some pretty neat images with that program. I coloured B&W movie images I scanned. I scanned myself then added me to different movie scenes I scanned ("hey, I didn't know you were in The Godfather"). They looked pretty realistic too - composite blends nicely and you don't see the pixels.