the only hang up i have with HKs are the heatspreaders, which i read are not as efficient as the heatspreaders on the HZs.
plus the HZ are only a few dollars more...and supposedly better overclockers, ie they are able to handle more raw mhz, but at higher latency.
but for me, as an amd user, raw speed isnt as important as low latency.
so...so...so...the stock timings on the HK are pretty awesome, and if you can manage to run them at 1100mhz @ the 4-3-3-5, well...that would rock.
i dunno. they both are pretty awesome.