The changelog on the PearPC site is broken. So for the sake of saving you a bit of time looking for it, here it is:
"version 0.5 (released 13. July 2011):
- slightly better code for lmw/stmw opcodes
- use "GNU as" instead of nasm
- use -mdynamic-no-pic on *darwin
- fixed some strict-aliasing problems
- JITC: AMD64 support
- compiles with gcc 4.3, 4.4, 4.5"