I rented, then purchased, the Ameda Elite. I exclusively pumped with it for about 15 months, so it got a lot of use. I use it once/day now for new baby.
They do have great re-sale value, even the very old ones, as I think there aren't many on sale out there and they do work well.
It was already a couple years old when I bought it, so it can get a bit squeaky, but it's not too loud. Depends what you mean by loud though. If you are in the same room, then yes you can hear it, but I never minded while at home. The loudest part is the click sound to turn it on and off. If baby was in same room, it would sometimes wake her up! I used it at work and assumed no one could hear it through a closed door. Well, no one ever said they could anyway!
As far as the dials go, I started off using both the suction and speed dials and would adjust them before and after milk flowed. However, after a few weeks I'd always keep it on the same speed setting and same suction level. My body just seemed to know what to do once I'd pumped a lot. I think the suction control is more important than the speed one, as you don't want it to suck too hard, as this could cause nipple damage or just make it uncomfortable, and therefore harder to pump.