Having now got my hands on a bottle, I can confirm it's every bit as good at lifting dirt and makeup as its more expensive, more organic counterpart. It does struggle a little with waterproof mascara, but so does the Melvita version, and a couple of passes eventually removes every last trace of mascara.
After use, skin is left feeling fresh and clean - amazing given how light the water feels. If I had to be picky, I'd say that the B micellar water is a little less hydrating than the Melvita, and that the packaging is a little difficult to operate - the plastic is a little too inflexible and it's quite hard work to squeeze it to dispense the product. For the tiny price tag, though, these are small niggles.
Find B Pure Micellar Water at Superdrug now, where it'll cost you £4.99 for 150ml.
Disclosure: PR sample