I've not used TVPaint for photo editing, as Photoshop CS3 on my Mac gets that duty. But I have enjoyed getting all artistic with TVPaint and with ImageFX on my Amiga 4000 with CV643D graphics card. The last Amiga version of TVPaint is free now, and you can get it here...
http://www.amigau.com/c-graphics/tvpaint.htmImageFX can still be purchased at
http://www.novadesign.com/. Looks like Nova Design is having a half-off sale for Amiga software.
I also keep Brilliance 2 and DPaint 4.5 (never got 5) on my Amigas for pushing around pixels and 2D animation in standard Amiga modes. I have the last or one of the last versions of ADPro but mainly use that for file format conversion duties.
If you've got the graphics card, ImageFX is worth the money. And TV Paint is totally free including a nice manual you can print out.