I've got a unique set of reporting tools, so I can offer a slightly different perspective on this update. I am, as far as I can tell, the first one on WebmasterWorld to report this update. Officially, it started rolling out at 9 PM February 23rd.
If I pay no attention to what I read about this update and only look at my own reports, this is what I see:
This update seems to have affected old, legacy articles and not new articles. That's why so many here on WW are reporting drops in traffic, we all have our prized content which is years and years old, and now they're being replaced in the SERP's by Google's favorite few.
It's almost like Google throwing out all the indicators they've had on the original content creators for pages over a few years old, and giving credit to their favorite sites, like eHow.
The articles that are effected on my site are original articles which have received hundreds or thousands of visitors per day for years, and they have been scraped constantly. eHow has copied my articles in the past, but I always out-ranked them. Now they out-rank the originals on my site.
Said another way, out of the 150,000 pages that make up my website, 40% of the traffic used to go to just the top 100 pages of my site. Now with those 100 pages no longer ranking, that accounts for a 40% traffic drop right there, but the vast majority of the rest of my pages are unchanged in rankings. I haven't found any articles on my site which are less than a year old which have been affected by this update.
The good news is that Google is crawling, indexing and ranking new content on my site just like they always have. (Hey, I'm trying to find good news here.)
I also have older articles which are seasonal, which only receive a significant amount of traffic for less than a week per year and therefore haven't been scraped and copied as much as other articles. These articles don't seem to be affected, either.
I don't see any correlation with the affected pages and backlinks.
If I were to name this update, I'd call it the 'Scrapers with Venture Capital Win!' update.