Thought I'd share my experience with this.
-Registered keywordsexactmatch.net in May 2011.
-Put up the site with 50 750-1000 word articles. The articles were well researched and written, but I made the mistake with overdoing with the wordpress tags system. Instead of just 50-60 indexed pages, I had like 400.
-By early August the site was up to 1,000 uniques per day and pulling in $60-$100 in adsense per day.
-The site lost about 70% of its traffic on October 14th (Panda update). Revenue dropped to $10-$30 per day.
-The main keywords didn't move much. I had lost all long tail traffic.
-After waiting until December 25th, I registered keywordexactmatchblog.com, then did change of address in WMT and 301'd the old site to the new one.
-The new pages quickly got indexed, while the old ones were de-indexed.
-I significantly cleaned up the site. It's same articles, but now there's just 58 pages indexed.
-150% Recovery of traffic and revenue started January 2nd.
Now I'm just working on getting the old backlinks updated to point to the new site, and waiting on the next panda update.