Yes you never really use that without the initial scale.
Initial scale of 1 basically means don’t shrink my layout to fit in your small viewport.
In this post I make some extensive demo tests as to what happens when initial scale of 1 is omitted.
It can be mind-bending trying to work out all the combinations but in the end for normal sites it really is just a matter of omitting the viewport meta tag if you have done nothing special for mobiles with media queries. If you have made the site responsive with media queries then add the viewport meta tag with initial scale set to 1.
More info:
http://blog.javierusobiaga.com/stop-using-the-viewport-tag-until-you-know-ho
http://www.quirksmode.org/mobile/metaviewport/
https://developer.mozilla.org/en/docs/Mozilla/Mobile/Viewport_meta_tag