I have had my eye on this for a while, but as I was quite content with my Mac foundation brush at the time, so I kept forgetting to purchase it. However I took the plunge and bought this before Christmas, and I am kicking myself that I didn't buy it sooner. I use it for concealer and liquid foundation and I adore the finish it gives. It took a few tries to perfect, but its worth the wait, my make up has never looked so good, and stayed on so long!
Tip I found on-line, the damper the sponge, the more of a sheer coverage you will have. So if you want a thicker coverage, towel dry the sponge a little more so its not as damp :)
If I had to critic it in anyway it would be that it stains easily. I have dark olive skin, and even though I wash it thoroughly after every use, it has stained the sponge (but I wouldn't care if it stained it bright green tbh, as long as it continues doing its job!).
I have also read reviews that it splits after 3-4 months use, which will be annoying, but I think it is worth the hassle of replacing it. Try it, you will never go back to using a brush again!