I ended up getting an Ameda Purely Yours pump when I went back to work with my son. It is much cheaper than the medelas (base price is only $150 instead of $250 if you don't get the accessory kit) and it works great. It's a very simple design, easy to clean, and the pump itself is small and lightweight (much more so than the Medela Pump-in-style). It's the only pump that's FDA approved to have no backflow or contamination of the milk. I have been really happy with it and was using it 3x/day for several months (am now down to 1x/day, only a couple days/week).
Renting a hospital grade pump is not cost effective if you're going to do it for months at a time, but if it's just for a few weeks, or to try it out, it's a good solution.