Last I heard it was 3.4kkeys/mhz, just a smidgen above the K5. Just remember that the mp6 has been, get this, announced "for the first time"......TWICE! Once when they thought they had a chance in entering the PC market, and once relatively recently (within the last two or three months) when they entered the appliance market.
While it was great per clock, remember that it maxes out at 250mhz.