One of the important features that got into the RV620 / RV635 specification is certainly the PowerPlay marchitecture, which will probably make these cards quieter and cooler.

This marchitecture can down clock your card while in idle and save some power, as well as make it quieter.

At 55nm the thermal readings got even better, but OEMs and System integrators really prefer it to stay even cooler than it was before. Radeon HD 34x0 will be a good choice for video freaks and casual gamers, as the card will do well in both.