They are in my opinion very easy to use, although a bit more fiddly than your bog standard box colours. You need to grate the caca block and mix it with water - the trick here is to get the right consistency. Some people find the application messy although I have to say I haven't ever found this to be the case, certainly no more so than colour in a bottle. You will need to leave the henna on for a long time - I would say a minimum of 2 hours. I usually go for around 4. The beauty here being that the colour isn't bad for your hair, so you don't have to set a timer to make sure you don't fry your hair
The messy part IMO is the rinsing. I am fortunate enough to have a closed in shower with good pressure, which makes it easy. If your shower has low pressure or you have a lot of hair (mine is short-ish and fine) you might want to consider soaking it for a few mins in the bath before actually showering.
The vibrancy of the red tones last at least a good month, and I find that the growth line isn't harsh at all, but that could also be because the colour I use isn't miles off my natural colour. Basically the colour lasts easily long enough for growth to be an issue rather than fading. I also find it makes my hair really glossy.
I don't think I'll ever stop using this hair dye
