I did a really whole lot of research on these and was just about to buy a Pump in Style when I found the Ameda Purely Yours. Don't waste money on a Medela. Yes, they are good, but the Ameda is EXACTLY the same thing with the same everything except for just a couple of things: It's quieter, it's motor only weighs 1 lb (as opposed to the 7 lbs of the Medela), and it's much MUCH smaller and easier to carry around (just looks like a purse) OH AND MOST IMPORTANTLY it's much cheaper (like 100 bucks cheaper!). I used mine 3 times a day for 12 months with never even the slightest problems. I'm pregnant now, and I will continue to use my same one.
I also bargain hunt, and the cheapest place you can find it (which also has free shipping) is http://www.healthchecksystems.com/ameda-breastpumps.htm You can even do a comparison to the PIS if you'd like to see how they have the same features. The Ameda actually has a little bit stronger pump, though. Good luck, and I hope you find what works for you.
OH! It takes 6AA batteries, and I only had to change them out one time in the 12 months!!