In recent years Field-Coupled devices, like Quantum dot Cellular Automata, are gaining an ever increasing attention from the scientific community. The computational paradigm beyond this device topology is based on the interaction among neighbor cells to propagate information through circuits. Among the various implementations of this theoretical principle, NanoMagnet Logic (NML) is one the most studied, due to some interesting features, like the possibility to combine memory and logic in the same device and the possible low power consumption. Since the working principle of Field-Coupled devices is completely different from CMOS technology, it is important to understand all the implications that this new computational paradigm has on complex circuit architectures. In this chapter we deeply analyze the major issues encountered in the design of complex circuits using Field-Coupled devices. Problems are analyzed and techniques to solve them and to improve performance are presented. Finally, a realistic analysis of the applications best suited for this technology is presented. While the analysis is performed using Nano-Magnet Logic as target, the results can be applied to all Field-Coupled devices. This chapter therefore supplies researchers and designers with the essential guidelines necessary to design complex circuits using Nano-Magnet Logic and, more in general, Field-Coupled devices.