Its also slow and can add a lot of time to renders. If you use it, try to keep the setting at 3 or below and drop the envelope to ZERO for portions you don't need to super size... oops, I must be hungry, I mean supersample.

The only time supersampling helps with the appearance of better resolution is if you're changing pixel ratio from odd, non-divisible values. If you use blur or something akin to that in your media, it will also assist there, but that's it.

"if you're changing pixel ratio from odd, non-divisible values"

You meant, swithching between frames (or clips) that go from 720x480 to 420x280 to 655x480 and such?
In my mind, the only reason to use it was to "create" more frames between, say, frames from a clip I stretched to more than its limits... Like the Resample switch we get on each clip but with adjustable/more powerfull controls.

Wow. I'm glad to read that about resolution.
I'll try since I never figured it out. Could be usefull to match some different clips.
In fact, the rare occasions I used it was to create effects so I didn't figure out many things about that.

... but if it is so, you super-sample in transitions (easy in cross-fades) ? How do you go with a cut? A real quick jump (to "super-sample") on the cut that happens, in a one frame space?

You'd set an envelope point, just like with any other envelope. Zoom in deep to get to a frame level.

Is supersampling useful at all in converting between the different frame rates of PAL and NTSC? How about in generating more frames from 15fps multimedia clips imported into a DV project?

No. It only affects motion created in Vegas, such as animated textures from the media generator or Pan/Crop or Track Motion movements.

On the other hand, the normal resampling function is very useful for converting frame rates.