I have 2 niche sites (little under a yr old) that have also been affected. One lost 50% traffic on April 27th and the other on April 28th. Traffic remains low, although it has improved a little since 6PM EST May 1st ( as noted by another member here as well).
I'm hoping this is similar to what happened to another site of mine on May 15. That particular site lost most of it's traffic and rebounded with 3x more traffic about 10 days after that. SERP wise my two affected sites remain the same if not better but traffic is much lower (probably very long tail phrases ). I am confident things will change for the better, if not then I might feel compelled to break something. These sites are clean, were slowly progressing and are unique, helpful and informative.