I usually see if it's necessary to upgrade to newer drivers before even thinking about doing it. If I don't have any problems with my current drivers, heck they can stay for the next 3 years.
Yeah I only install new drivers if they claim to be beneficial. all those stories of v4.5 are terrifing. I installed them and had no probs but went back to v4.49 just in case.
Apparently Via did a quick fix on the 4.51 drivers by defaulting the aperture to 32mb. Wouldn't that end up hurting performance in certain situations though ?