I was told the same thing and got the rental. Now I wish I had just listed to Nona and Lenore and Kerri and EVERYONE. While I'm only at 3 - 5 ounces per day, this a big improvement on the 1-2 ounces I was getting with the hospital grade pumps. I've also heard they can damage your breast tissue they are so strong.
Trust me on this one, listen to the ladies here. Beware, your LC will be irritated when you tell her, "I'm going with the PIS because of the advice on Lenore's website." I've gotten that reaction from three local LC's, and all three are very well known.
Hope this helps!
Aloha,
Christina