Another big fan of the PIS. I have the old style and it works great. I imagine the new could only work better. My sister and I have shared it, so it's on the 4th child, currently. You can often find good deals on line to purchase for much less than at BRU. Drugstore.com sometimes has specials, but just do a google search. I waited to buy until I was sure breastfeeding would work for us. Many of the on-line sites have free overnight FedEx on the pump. If nursing didn't work, I knew I'd want to pump exclusively for at least a while and in that case would have rented a hospital pump since they are supposed to be more effective.
We use the Playtex bottles with the disposable liners and they now make a pump adapter for the PIS so that you can pump directly into the liners! It comes with 4 sealing disks to freeze. I don't use it much for freezing, but it is AWESOME for the milk that will be used the next day. I pump "one side" into the liner and the other side into the plastic Medela bottle that comes with the pump. When I'm done, I combine into the liner, seal it and stick in the fridge for the next day to drop right into the bottle - no pouring or wasting of the milk. (Then I adjust total amounts for each bottle as needed.) For the milk I freeze, I got 25 reusable soft 4 oz. plastic bottles to store a lot of it. The extra beyond that I have frozen in Lansinoh bags (I've been building up a 'stash' for when I go back to work full time). I also like the Medela bags. I tried the 'First Years' bags and Gerber bags and really don't like those. As for basic Ziplock bags, I personally wouldn't use them for a really young baby when it's nice (IMO) to keep everything sterilized. But by 6 months, I can't imagine unsterilized new bags would be worse than what they're getting off the floor from rolling around or from whatever they're teething on at that point (yes, my 5 month old daughter is very adept at finding shoes from across the room and latching on!)!