Different technology. PyPy/RPython is a more "high level" approach built on top of metatracing while OMR is more low level and geared towards method-at-a-time JIT. (I might be wrong. I worked more with pypy but only know OMR superficially)

Don't know yet. IBM has a CPython-based JIT using OMR but it hasn't been publicly released yet.

Ruby OMR is a little more public and from what I can tell gets about a 30%-200% speedup. They basically just stapled OMR onto the regular Ruby interpreter, so there's nothing fancy going on yet and those numbers will definitely get higher.