My hairstylist girlfriend gifted this to me 2 years ago for Christmas, and I've been loving it since. First off, the brush is absolutely beautiful! The handle is made from real African mahogany hardwood, and the boar bristles are 100% pure and natural. It looks and feels expensive. I've been using it everyday, and only 1 bristle has fallen out. So it's a very high-quality, well-made brush.
For reference, I have waist-length hair that's in between thin and full - a lot of hair that are somewhat thin from bleaching. Compared to other boar bristle brushes that I've used, the Kevin Murphy brush strikes the right balance between soft and hard - gentle enough to not pull on my hair and strong/long enough to untangle the knots quickly and effectively. This bristles on this brush can actually reach my scalp, unlike other brushes. So it's good for massaging my scalp. Although the website says that you're supposed to use on dry hair for best results, I like to brush my hair while it's 50-70% dry to smooth out my naturally straight hair. Even when I brush somewhat wet hair, the brush doesn't snap my hair and does a really wonderful job of smoothing it and minimizing fly-aways.
This brush isn't cheap (about $60 CAD but you can buy it from Amazon for £18), but it's really worth the money. If you're looking for a boar bristle brush that looks gorgeous and performs well, try this one.