Seo Sangyheon ran some tests, and discovered that IronPython 2 is either faster or slower; depending on what platform it runs on...
IronPython 2 compared to IronPython 1:
Mono 1.2.4+: -32%This shows that IronPython 2 makes heavy use of some of the improvements in recent versions of the CLR runtime.
MIX07 (Orcas?): +12%