I like it a lot. Many of my backgroundless cels 
have photographs as BG. I don't have them scanned 
into my gallery that way because I wasn't sure 
how people (especially the purists) felt about 
it. 

I find that photos work great for outdoor scenes 
but not as well for indoors. I can get the 
lighting direction and colors OK for these 
scenes, but I have never been able to get the 
shadows the character(s) are supposed to be 
casting on the walls correctly.