I have the xs/m and I really like it. However like the previous person said, do remember they are *ahem* American sizes, I'm quite tall for a girl (5ft 9\") and the s/m is almost too big. I have all the straps tightened as tight as they'll go, and have had to cut off about a foot of extra strap from the waist ones. Also, the wonderpro isn't CE approved so technically you can't wear it in competitions in UK / Europe, however it has US coastguard approval so I wouldn't be even slightly worried about using it...
Other than that - super comfy, floats me nice and high, good buy. Defintely recommend it.