I used it with henna because it supposedly makes it darker on hair and reduces the orange tones. I never used "real" henna alone so I'm not sure if it did the work. The color turned out a nice dark red on my light brunette hair though.
Having tried henna and indigo in various proportions over last couple of years to cover grey temples in my otherwise dark brown hair, I felt the build up of near-Black was too harsh for my aging skin tone. After some research I decided to mix 40% henna and 20% each of amla, cassia and indigo. Result : a beautiful rich flattering chestnut that covers the grey, blends in and leaves my hair in soft, glossy condition. The colour took about 3 days to settle to its current tone. Will continue - very happy, and the very dark ends will grow out with regular trims.
I bought this because I have fine, grey hair, already use cassia and wanted the body and condition you get from henna. I loved the thickness and condition I used to get when using henna, just disliked the marmalade coloured result. I mixed two parts cassia to one part amla with water, left it for about 6 hours (as per instructions on a website which promised the result would be luxuriant hair which would be darker than achieved by cassia alone). I applied the mixture to my hair, put on a hat and left it overnight. The next morning I washed it out with conditioner. The result was that all the previously applied cassia colour had been stripped out of my hair. The hair had gone back to being a dull, cold grey. As for the condition - it was very fine and fly-away. There was no improvement and I would argue it was drier and finer than before. I know that amla is considered to be the best hair conditioner, but it isn't as good as henna or cassia.
I don't know how much of a difference the amla powder makes as I am using it for the first time. However, I mixed it with henna and landed up making the paste too watery, so I was able to leave the paste on my hair for 1 hr only. I still managed to get a good colour and it was easy to wash out the paste from my hair. I will continue using the amla powder with the henna powder.