What filters to use?

[BluDChyLD]

Hi,
I've never bothered applying any of the video filters in virtualdub, are there any "must use" filters which really improve image quality? I've seen temporal smoother being mentioned alot, what does that do?
Thanks,
BluDChyLD

[FactorM]

it increases the compressability, and using it with values of 1 or 2, changes in picture quality are not noticable that much.