depends if you want to scrub your paint in a kitchen or have a really hot and steamy bathroom. It is a more durable paint but it depends what you need.
I have used it next to a shower with no flaking off the walls (which would happen with normal emulsion) but the key there is leaving it to dry in a very dry environment (no baths or showers for at least 72h!)
All K&B paint is,is water-based (acrylic) eggshell. The dulux trade eggshell that you can get mixed is a better quality version and you can get any colour you like (but never expect them to mix more in the exact same shade if you run out! it's not possible with the machines they have.)
I'm not convinced - we have it in our bathroom and yes, it's fine and durable, but it's horrible to paint with and more expensive. I think ordinary emulsion would have been fine to be honest. We used ordinary emulsion in the kitchen with no problems.
we used normal paint in our bathroom and it cracked, made a right mess. we moved house, but if we'd stayed, all the walls would have needed sanding and re-painting properly. i gave it another coats of normal paint over the top to hide it when this first happened, but it cracked again in a matter of weeks
The problem with matt paint is that it is porous. its the rough surface that scatters the light and makes it matt. but water can get into the pores and lift the paint off the walls.
if it is for a kitchen I would say don't worry, the new gen acrylic matts are so cleanable you wouldn't have a problem but as far as I know they haven't cracked a water resistant matt emulsion yet. I think that dulux "real life" has a matt finish. that should be fine for a kitchen so long as you don't fry chips every night without an extractor..... its pricey stuff but every time i've gone for cheap paint i've ended up spending more on repainting than it would have cost to by quality paint. I've just used "real life" paint for first time in our dining room and it went on well but is yet to be tested by dd for durability.