I like to frameserve out to Virtual Dub...specifically using Donald Graft's Smart Smoother filter to remove grain...I've been able to remove all traces of grain even with my XL1s cranked to +12db with low light wedding work. Verbiage from his site about the filter-- "This filter performs structure-preserving smoothing (blurring). It is ideal for removing video noise as well as MPG/JPG blocking artifacts. The really exceptional feature is that far from blurring image structure (edges, corners, etc.), it actually sharpens them somewhat!"

Give it a try...you will probably be surprised as much as I when I stumbled onto this process....

http://neuron2.net/

the median filter in vegas is pretty good, but why it is so slow i'm to sure .. but it does do a very good job ...

i also frame serve out to smart smoother or other filters in other apps which is much quicker most of the time if nessessary ..

If you are talking about film grain reduction, then Applied Science Fiction (recently acquired by Kodak) has some of the best technology available. Their GEM technology is absolutely miraculous. I use it all the time for film scans (still photos). I don't know whether it could be applied to movie film, other than one frame at a time.

The GEM technology goes beyond simple pixel averaging, and therefore results in very little softening of the image.

If you want ot get rid of "snow" type noise in video images, you are much better served to use a temporal filter (one that looks at multiple frames and then averages) rather than a spatial filter (one that looks at adjacent pixels in one frame and then averages). There are many such filters for both VirtualDub and for AVISynth. Unfortunately, the Vegas plugin interface apparently does not permit external plugins to operate on more than one frame at a time, so until this changes there will be no solution that works inside of Vegas.

Median is slow because it does a full convolution. (I think it is box unless you check circular processing, which is full.) This means it must go through every pixel, and for each pixel examine every pixel around the current pixel within the radius of the range settings. Higher range settings get exponentially slower in a typical median filter.

More info on median filters here if you are technically inclined...http://www.cee.hw.ac.uk/hipr/html/median.html

Check out the Algolith pluginsand/or Grain Surgery (not sure if they have either one for Vegas)

Both do an outstanding job of grain removal.