You are right. The 5 fps vs. 3 fps is something I don't understand, either.
There is only one reason for me to prefer the E-P3, that is its thickness. The E-PL3 seems to be much thinner than my E-PL1 which may be more problematic when I use the camera with my Canon FD 100mm macro lens on a tripod. So I should go for the E-P3, if I bought one of the new cameras. However, since the sensor does not seem to be as superior as I hoped, my E-PL1 does everything for me what I really need. The better AF is fine, but I shoot with MF lenses very much and I have never missed a faster single focus AF with my AF lenses. If the E-P3 had an articulating screen, I would buy it. If it had a much better sensor, I would buy it. But since this is just a small incremental upgrade, I am not so sure that buying the E-P3 makes sense for me. But I will wait until I get some raw files which I can develop in Lightroom, before I make the final decision.