The mega O.I.S is very impressive and I can get reasonably sharp images at 200mm and 1/30s!
From an IQ standpoint, I am very pleased so far: wide open, the lens is pretty good from 45mm to around 100mm and still pretty decent beyond that.
Overall, I am very happy with the performance of this $280 lens.
Some comments about using this lens with the Olympus E-P1.
The good news is that the AF is almost as fast as with the GF1 (feels as fast for me but don't want to start a milliseconds war here so this is why I am saying almost as fast).
I also quickly tested Olympus IBIS vs Mega O.I.S. and I would say that at 200mm, the in lens image stabilization (MEGA O.I.S) does better than the sensor IS. Not much, but enough to make a difference. I would roughly say 1 stop difference. but in any case, bot IS systems do an impressive job.