I wouldn't worry about using the meta title tag. It almost certainly has no SEO value since it is redundant with the true
<title> tag but unlike the
<title> it has no effect on the page's content or browser display so it is ripe for abuse and serves no actual purpose content wise. (FYI, that's also why the keyword and description meta tags have no SEO value).
<speculation>If I was going to attribute any meaning to that meta title tag it would be to convey the actual title of a document as opposed to the
<title> tage which may be used simply to display a title in the browser window. In other words the author will use the
<title> tag to make sure the user sees something helpful in their browser title bar and the meta title tag provides the user agent with the true title of the document. I can't think of too many cases where this would be useful but it may be possible.
On the side, I wonder why the StackExchange sites don't use the meta description tag? Since it may be what is displayed on SERPs it can only be a good thing. Then again, they tend to do so well in search anyways due to their popularity (aka link popularity) that they simply may not need them.