My 7970's are upclocked (not overclocked
) via bios edit. Before this, my AMD-reference HD5870's were slightly uplocked (over the reference clocks) from factory by Asus (cherry-picked reference gpu's) in the bios. Before that, i (slightly) overclocked but mainly profiled the fan-behaviour to be more effective on my AMD-reference Club3D HD4870X2 using Riva Tuner profile which worked very well. At some point when the driver wasn't supported i decided to keep the card running at stock. No more hassle, and the games ran just as well. Before that, i overclocked my HD4870 slightly only using AMD Overdrive, that was until i bought a 4870X2! 
Before that, i upclocked my HD3870's only using AMD Overdrive. Before that, i upclocked my X1900XT only using AMD Overdrive.
I have never killed a videocard through overclocking!
From MSI Afterburner release notes:
Download (msi.com) latest versionKnown limitations:
- RivaTuner Statistics Server can be incompatible with some third-party On-Screen Display software (e.g. XFire or Steam In-Game Chat). The limitation is not specific to our product, many third-party products are designed to be the only On-Screen Display products in the system and to block their own functionality when any other On-Screen Display software is running
- Anticheat systems of some online games may restrict On-Screen Display usage and block connection to the server when the
RivaTuner Statistics Server is running- RTV1 encoder performance in 64-bit applications is currently lower than in 32-bit applications
- Stealth hooking mode is currently not supported in 64-bit applications, so it is strongly not recommended to run other 64-bit On-Screen Display software in conjunction with RivaTuner Statistics Server