Absolutely love them if done correctly. I have seen some outstanding work of civil war era colorized photographs. I used to have a small business selling historical / vintage prints. Using photoshop I would restore and improve the images. I also played around with colorizing some of them with mixed results. It seems to be part art and science using photoshop. It is a bit time consuming depending on the image. I never thought of colorizing WW2 photos. Perhaps I can try to do one. I love to see good color WW2 images it helps me with my fine scale models I build.
I agree with Wasteoid, if done well they really add to the image. When they first started coming out in the 1990s they were often grainy and crappy looking, now they often look so good you wouldn't know they had been colorized, you'd think they were originally taken in color. The Civil War photos above are a great example.