The rubber mat is nice and the scale itself feels fine, but I've never seen a scale this slow to update. The 0.1g accuracy is highly questionable, the numbers seem to only really update every 0.2g and even then they change if you take the cup off and put it back on. Spend a little extra on something higher quality.
2 stars because it's at least cheap and I can use it as a general kitchen scale, but stay far away for espresso or any coffee application really.