I checked my stats this morning and visitor numbers have plummeted. My domain name has no bearing on my keywords, and I do not have a spammy website. I've maintained it for about 7 or 8 years, and it's always done well. I keep it up-to-date, and have designed and written it myself. I have great natural backlinks (many one-way), and have never paid for traffic. Having checked there was no downtime, I saw this thread and have seen they have rolled some updates.
When I search for my website using my usual keywords, I have gone from page 1 to page 3 or below, and have lost about 70% of my traffic. I don't know if it will continue indefinitely, or if I can appeal, but I feel I have been very unfairly hit, and am also devastated as my website is my main source of revenue.