Psyco is unmaintained, the developer of it (Armin Rigo) is working on PyPy (a Python compiler written in Python) instead: http://codespeak.net/pypy/dist/pypy/doc/
They are already seeing quite nice results for computation-heavy benchmarks with the (tracing) JIT: http://speed.pypy.org/comparison/
While psyco is great you can't really rely on it anymore since it's 32-bit only. Though simply using it if it's available does help slower, older machines that need the speedup, so I wouldn't write it off completely.
Hopefully Unladen Swallow will make even more progress over the rest of the year.
They are already seeing quite nice results for computation-heavy benchmarks with the (tracing) JIT: http://speed.pypy.org/comparison/