if you already have your favorite powder brush and are happy with it, and can't part with the money, you don't need this brush
i picked up a 183 on the weekend. i am in love with this brush. if you are a brush lover or require a variety of tools for every/different look(s)...this is one you need for your collection. it gives a burnished finish with powders on skin. the finish is beautiful. i am thinking about getting another 183, as these are LE.
i love my 182, which gives a polished, classic finish but the look is different. the 188 and 187 give a more light and natural application and are more multi-purpose (i like my 188 and 187 for cream or powder blush,and highlighters. i prefer the other brushes for loose/pressed powders)
you really have to try it and see the difference. though the difference is minor to some...if you have great skin, this can make your skin look that much more amazing.