I've built several layouts with both Ross/Gargraves and Atlas track and turnouts. My experience with the Atlas turnouts was that the switch machines were delicate and unreliable, and I wound up removing the Atlas switch machines and installing the Z Stuff D-1000s, which worked well. I am currently between layouts and hope to build another (hopefully my last) in the next year or so. Given my experience with the Atlas switches, I expect to go back to Ross/Gargraves.
Reliability is key and will save a LOT or cursing and frustration. George's recommendations above are spot on. Always test the switches on you bench BEFORE installing them on the layout. And always make sure you have some way of reaching all of your switches for maintenance and to tend to derailments.