P: Rendering issues: pixelated image while making adjustments or brushing

Lightroom 4.3 final (on Windows 7 64bit, with an ATI Radeon HD5450, latest Catalyst 12.10 drivers) gives me some really weird rendering issues in the Develop module that were not present in the RC ("beta 6").

As long as I hover over the knob of a slider after making an adjustment, the image is not properly updated/refined and stays in an unrefined/pixelized state. This happens with ALL sliders in all sections of the Develop module. It was working in LR 4.2 and LR 4.3RC.

What's more, when I use the local adjustment brush, I see a MUCH larger area than the size of the brush affected initially as I add a brush stroke; only when I release the mouse button the adjustment is rendered correctly. Again, this too was working in LR 4.2 and LR 4.3RC.

Things I have tried: update/revert the graphics drivers (I tried a total of FOUR different driver versions). Update/revert the mouse driver. Delete the ACR cache. Start with a fresh catalog and no plugins, just adding something like 100 photos. Nothing helps.

To say the least, it is ANNOYING that something like the rendering in the Develop module is changed from an RC to a final version when it has such a MAJOR impact. It renders LR 4.3 final practically unusable for me; I've reverted to the 4.3 RC (which is faster and more responsive than 4.2 was).

Adobe Forum thread: http://forums.adobe.com/message/4926364