I have overclocked as far as:
Overclocked at +175mhz // +500mhz // 110% power target // +37mv overvoltage.
Shes got more in her but I have yet go any further. Ambient temps 70f.
I've read the hybrid version keeps temps around 45-50c under intense load. The hybrid is a better unit, not for an extra $70 bucks though.