Got my S5 yesterday and was so excited to use it. I've only used it twice but so far I'm loving it and think it's actually giving me greater output than my Unimom Opera, which is a FANTASTIC double electric pump, similar to spectra.
I got this as an easier way to pump more frequently during the day to help increase my supply. Pumping more frequently when it requires me to sit at a table while trying to take care of my almost 2 month old was near impossible. Still playing around with the settings but I love that there's a mixed mode of massage and expression to help keep milk flowing.
My only complaint is its difficult for me to see when milk stops flowing while the unit is inside my bra, so I don't necessarily know when it's done. First time I left it on for 15 minutes (normally only need to pump for 10). Second time I did 20 minutes. I felt a change in suction in the last few minutes the second time I pumped and read another review saying it auto adjusts suction when breast is near empty which i think is really cool! I will be returning to work in 2.5 months and excited to take these babies with me!