If anybody has simple and beautiful :) use cases of QEMU please share. I used it to run Debian Squeeze MIPS images, so that I could have gcc output in MIPS assembly.
Many FPGA CPU simulators attempt to be cycle-accurate for the purpose of architecture development, where the emulator has the leeway of treating instructions as atomic units and abstracting the rest.
It's a startling upgrade over using Adobe BrowserLab or local virtual machines, which were our previous strategies.
Making a multiboot-compatible kernel image that you can boot with QEMU (and with real iron using GRUB) requires only a few dozen lines of assembly code and a simple linker script.