If you have to release some artwork in a vectorial format (SVG, EPS, AI or PDF) and want to set it so that it can easily being scaled, make sure you have all the contours stoke converted to shapes. I know it will take more time, but you'll gain quality in the long run.

Let's say your contours stoke is 2pt. thick.
When importing and scaling your final work in another editor, some will keep the contours stoke proportional (2pt. x 2 = 4pt.), some won't (2pt.).

If the image doesn't show, go to the gallery.

That can completely change the way the arwork looks if you created a visual effect based on the contours stoke.

So always make sure that at some point you do convert the contours stoke to a shape.

If the image doesn't show, go to the gallery.

When you talk about contour, you mean stroke right? Viewers shouldn't change the porportions of the stroke when scaling--it's true that some editors might though. In Inkscape this is controllable by toggling the appropriate affect on the tool control bar when is selected.

You're right, though. If your releasing something to a client, converting stroke to path will make sure they can't mess things up.