plt-scheme gets a JIT Compiler - which should provide a significant boost for DrScheme, the best Scheme in the world. So far, it has been a purely interpreted system with its own virtual machine - and that was already damn fast. But a JIT compiler can bring a lot, especially for larger string mountains or list gobblers and number tangles. It will be exciting to see how this compares to e.g. Gambit-C and Chicken.