The layer system has been replaced with a multi-axis grid system. By pressing [B] in in editor it will toggle through different snap and grid modes for entity placement. It will display in the lower right of the editor which mode you are in. There are 5-unit and 100-unit grid snaps available and this includes the vertical direction as well. It takes some getting used to and isn't as simple but it offers more freedom than what classic had. It's still a bit of a work in progress though, so it can be easy to overshoot the layer level you are intending. This will be improved over time. When the conkit is eventually out, it will simplify building certain types of structures.
Gigabyte P67A-UD4-B3, Intel Core i7 2600K, 16GB Corsair DDR3, EVGA GTX 970 SC, Win7 Pro 64-bit SP1, Primary monitor @ 1920x1080, secondary monitor @ 1024x1280