Need a bit more info - what system / OS you running this thing on, ie. custom box or a one from a major retailer?. What are you using to report the core and memory speeds? - a 3rd party app or ATI's Catalyst software
As far as speeds - it depends on what yardstick, they use to measure the speed. There was some confusion comparing the GDDR3 to the GDDR4 memory clock speeds - basically, GDDR4 is reported at half its speed compared to the GDDR3 cores. No worries - the 3870 is spec'd at 1.12-1.2GHz on the AMD/ATI website. Basically some places are listing the "effective" clock speed. This is to make a direct comparison between the different cards running either GDDR4 or GDDR3 - they are trying to change it to a common yardstick, as many are confused as what is the correct memory clock speed.
I too have some several reviews that have the mem clock speeds at 2200 - 2400MHz, some have made corrections and brought them back to the spec 1.12-1.2GHz ratings - some have not.
I also am in the market for one of these badboys - already have a 8800 GTX for "work" related needs, but the 3870 should prove to be very competitive at a fraction of the cost - perfect for the detail rich, immersive games out there. Maybe by tax refund time - new system + new WS monitor (the big ones have been dropping in price like crazy - might have to upgrade to a 22"-30" one for grins now ). Just have to decide what flavor of processor I want to run.