this essay on Slate.com by Michael Erard, author of Um... Slips, Stumbles and Verbal Blunders, and What They Mean. You have to imagine that I'm going to like an article that backs up my view of "ums" and "uhs" NOT being the downfall of civilization as we know it.
Here's an excerpt:
"People have been pausing and filling their pauses with a neutral vowel (or sometimes with an actual word) for as long as we've had language, which is about 100,000 years. If listeners are so naturally repelled by 'uhs' and 'ums,' you'd think those sounds would have been eliminated long before now. The opposite is true: Filled pauses appear in all of the world's languages, and the anti-ummers have no way to explain, if they're so ugly, what 'euh' in French, or 'äh' and 'ähm' in German, or 'eto' and 'ano' in Japanese are doing in human language at all.
In the history of oratory and public speaking, the notion that good speaking requires umlessness is actually a fairly recent, and very American, invention. It didn't emerge as a cultural standard until the early 20th century, when the phonograph and radio suddenly held up to speakers' ears all the quirks and warbles that, before then, had flitted by. Another development was the codification of public speaking as an academic subject. Counting 'ums' and noting perfect fluency gave teachers something to score."
Enjoy the article, and if you want to know what I think about "ums," here's a blog post or two.