The overclock is ok. 

Sapphire also makes a 4850 with 1GB of memory. This is the first 4xxx series with more than 512MB of ram aside from the X2. Its a more niche product than an overclocked card, but its great seeing Sapphire step up and doing it! For anyone doing GPGPU memory speed may not be all that important (particularly anyone doing double precision floating point work) but the memory size will make or break a lot of applications.

The standard 4870 overclocks to 785/1050 out of the box and is still pretty quiet....seems like money for old rope to me....