The Avent Isis is a God send, let me tell ya! I first owned an electric Pump In Style. While I was pregnant I also bought the Isis. I decided when I wasn't getting much milk regardless of how much I pumped, I'd try this manual pump that I heard other breastfeeding mothers on message boards talking about. I found one through Craigslist and paid very little for it. I figured if it didn't work or wasn't that good, I didn't lose a lot. Luckily, I didn't have that problem!
This pump is super easy to use. It's easy to assemble and the instructions within the package are really easy to follow. It's of course nice to have the bottles that you can attach and pump your milk directly into.
The thing I loved most about this pump is that although it's manual, it's not difficult at all. I found that this manual was easier than my electric and I'll tell you why. With the electric pump, you have to hold each piece of to each breast. There is no hands free about it. Whereas with the manual Isis, you can pump one handed and have one hand free. The pumping is so easy it almost feels broken (don't worry, it isn't!). It literally feels like you aren't even pumping yet the suctions is really good.
This manual pump brought me to let down so much better and more often than the Pump In Style that I would recommend this pump before the latter.